Anti-Lock, Rear

Inspection and Verification

System Pre-Check

NOTE: It is important that this procedure be performed first. Failure to do so can result in incorrect diagnosis of problem, wasted time and improper replacement of components.

The System Pre-Check is used to screen a vehicle for relatively simple diagnostic service, such as loose connectors, blown fuses, etc. However, the System Pre-Check is also used to prepare the vehicle for further diagnostics. In addition, warning light concerns are dealt with in this check.

NOTE: The anti-lock electronic control module (2C018) is commonly referred to as the RABS I module or, on later models, the RABS II module. This service procedure is written for RABS II systems (as opposed to RABS I systems). The RABS II system is standard for F-250 Heavy Duty and F-350 vehicles. In the event that you are not sure if you have a RABS I or a RABS II system in the vehicle, check the anti-lock electronic control module part number. Anti-lock electronic control module part numbers will begin with either: F3TF-2C018- or F3UF-2C018-. All other part numbers should be considered to be a RABS I anti-lock electronic control module. If the vehicle has a RABS I anti-lock electronic control module, refer to the service manual for that model year vehicle.

The RABS II uses both the red BRAKE and yellow REAR ABS instrument panel warning lights to alert the driver to a system malfunction. Both lights must be working properly to assist in concern diagnosis. The steps listed below must be followed prior to beginning the RABS II diagnostic procedure.

Vehicle Setup

 WARNING: PLACE BLOCKS BEHIND THE REAR WHEELS (1007) AND IN FRONT OF THE FRONT WHEELS TO PREVENT THE VEHICLE FROM MOVING WHILE THE SYSTEM PRE-CHECK IS BEING DONE.

For 4-wheel drive vehicles, shift into 2-wheel drive. Drive the vehicle to a level area, and place the shift lever in PARK for automatic transmissions (7003) and NEUTRAL for manual transmissions. Turn the ignition off, set the parking brake and turn on the running lamps. Place blocks behind the wheels.

Continue with the System Pre-Check.

Warning Lamp Indicators

The red BRAKE warning light is constantly monitored by the anti-lock electronic control module. If the red light illuminates, the anti-lock electronic control module will disable the RABS II system and turn on the yellow RABS light. For this reason, diagnosing and resolving any base brake concerns illuminating the red BRAKE warning light will, in most cases, resolve a perceived RABS II concern.

Brake Light Self Check

The red BRAKE warning light is used to indicate a low fluid level condition or parking brake applied condition. To check this light, insert the key in the ignition switch (11572) and turn it to the START position. The light should glow in this position. If it fails to glow, go to the Symptom Chart.

Allow the key to spring back from the START position to the RUN position. At this time the BRAKE warning light should turn off. If it does not turn off, recheck the parking brake to make sure it is fully disengaged. In the event that the BRAKE warning light remains on, go to the Symptom Chart.

Rear Anti-Lock Warning Light

The yellow REAR ABS warning light is used to indicate a malfunction and a deactivation of the RABS II system. To check this light, first follow the procedure above for red brake warning light self check, and allow the key to spring back from START position to the RUN position. The yellow REAR ABS warning light should perform a self-check by glowing for approximately two seconds and then turning off. If it turns back on and does not flash, then a system concern has been detected. Refer to On-Board Diagnostics, Diagnostic Trouble Codes, Retrieving. If it fails to glow, go to the Symptom Chart.

On-Board Diagnostics

 CAUTION: Care must be taken to connect only the black/orange stripe wire to ground. Connecting the red mating connector wire to ground will result in a blown fuse.

Diagnostic Trouble Codes, Retrieving

Verify the key is in the RUN position (engine does not need to be running). Next, locate the black RABS II diagnostic connector. The diagnostic connector has two mating halves (one of which has a black/orange wire connected to it). Disconnect the two halves.

Attach one end of a jumper wire to the black with orange stripe wire side of the diagnostic connector. Momentarily ground the other end of the jumper wire by connecting it to a good chassis ground for 1-2 seconds. Grounding this wire should start the yellow REAR ABS warning light flashing. If grounding this wire does not start the yellow REAR ABS warning light flashing, go to the Symptom Chart.

The code consists of a number of short flashes and ends with a long flash. Count the short flashes and include the following long flash in the count to obtain the code number. For example, three short flashes followed by one long flash indicates diagnostic trouble Code 4. The code will continue to repeat itself until the key is turned off. It is recommended that the code be verified by reading it several times. This code will be used later for system service instructions. It should be written down for future use. Diagnostic trouble code 16 indicates that the anti-lock electronic control module detects normal system operation.

Diagnostic Trouble Codes, Erasing

The last step of the System Pre-Check always includes clearing the Keep-Alive Memory (KAM). To do this, simply turn off the ignition while the diagnostic connector halves are separated as described in the procedures for obtaining the diagnostic trouble code above, after which the diagnostic connector should be reassembled to provide KAM power to the anti-lock electronic control module. If at this time a valid code has been obtained, go to the appropriate pinpoint test for that code.

Symptom Chart—Rear Brake Anti-Lock Control

Refer to the Electrical and Vacuum Troubleshooting Manual for the connector numbers in the pinpoint tests.

NOTE: Use Rotunda 88 Digital Multimeter 105-00053 or equivalent to perform electrical pinpoint tests.

There are times when a customer concern will not cause the yellow REAR ABS warning light to illuminate or a code to be stored.

The symptom chart is intended to give the technician a starting point in resolving these types of concerns. The chart also describes conditions that will illuminate the yellow RABS light.

Please note that both the red BRAKE warning light diagnosis procedure and test drive are required prior to performing the tests in this section. Failure to perform these procedures will greatly diminish the effectiveness of this method of diagnosis.

Pinpoint Tests

PINPOINT TEST A: RED BRAKE WARNING LIGHT DOES NOT SELF CHECK

Description

If the red BRAKE warning light does not turn on when the key is in the START position, service the brake warning bulb system as required. The most likely cause of a nonfunctioning red BRAKE warning light is a burned-out bulb or an open fuse.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Open brake warning light bulb (RED)
• Open power fuse
• Open Circuit 640 (R/Y), 977 (P/W), 512 (T/LG), 531 (DG/Y)
• Open resistor/diode circuit
• Unseated fluid level switch connector
• Defective ignition switch

A1 RED BRAKE WARNING LIGHT/FUSE

• Key to RUN.
• Apply parking brake.
• Observe BRAKE warning light.

A2 CHECK FOR CORRODED FLUID LEVEL SWITCH CONNECTOR PINS

• Remove fluid level switch connector C170 located on brake master cylinder.
• Inspect both halves of fluid level switch connector for corrosion or connector pin backout.

A3 CHECK FOR UNSEATED CONNECTOR

• Firmly reconnect fluid level switch connector C170 located on brake master cylinder.
• Key to START.
• Observe BRAKE warning light.

A4 DIODE RESISTOR ELEMENT/CIRCUIT 531

• Disconnect fluid level switch connector C170.
• Connect jumper wire from diode/resistor side of Circuit 531 (DG/Y) to known chassis ground.
• Observe BRAKE warning light.

A5 MASTER CYLINDER FLUID LEVEL SWITCH

• Connect jumper wire from Circuit 531 (DG/Y) to Circuit 512 (T/LG).
• Key to START.
• Observe BRAKE warning light.

PINPOINT TEST B: RED BRAKE WARNING LIGHT STAYS ON WHEN KEY IS IN RUN POSITION

Description

Red BRAKE light on with ignition switch on and parking brake released.

Possible Contributing Component/Vehicle Wiring Faults

• Ground short on Circuit 977 (P/W)
• Ground short on Circuit 162 (LG/R)
• Damaged parking brake switch
• Damaged low vacuum switch (diesel only)

B1 CHECK IF BOTH WARNING LIGHTS ARE ON

• Disengage parking brake.
• Key to RUN.

B2 CHECK PARKING BRAKE SWITCH

• Key off.
• Disconnect parking brake switch from harness connector.
• Key to RUN.

B3 CHECK LOW VACUUM SWITCH (DIESEL ONLY)

• Key off.
• Disconnect low vacuum switch from harness connector.
• Key to RUN.

PINPOINT TEST C: YELLOW REAR ABS WARNING LIGHT OFF AND DOES NOT SELF CHECK

Description

The anti-lock electronic control module will turn on the yellow rear ABS warning light for 1-2 seconds after the key has been turned from the OFF to the RUN position. If REAR ABS warning light fails to flash, it can be caused by a burned-out bulb or an open fuse to Circuit 640 (R/Y). An open in Circuit 603 (DG) will also keep the light from flashing.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Open fuse Circuit 640 (R/Y)
• Missing power to REAR ABS warning light (open Circuit 640 [R/Y])
• Open Circuit 603 (DG)
• Burned-out yellow REAR ABS warning light bulb
• Terminal backout in the anti-lock electronic control module harness connector at Pin 7
• Harness connector not fully mated with anti-lock electronic control module
• Damaged anti-lock electronic control module
• Open REAR ABS ground (Circuit 530 [LG/Y])

C1 REAR ABS LIGHT 10 AMP FUSE

• Remove and inspect REAR ABS light 10-amp fuse.

C2 ANTI-LOCK ELECTRONIC CONTROL MODULE HARNESS CONNECTOR

• Check to make sure harness connector C277 is fully plugged into anti-lock electronic control module.

C3 ANTI-LOCK ELECTRONIC CONTROL MODULE GROUND

NOTE: When checking resistance in the RABS system, always disconnect the battery to starter relay cable. Improper resistance may occur with the vehicle battery connected.

• Check for good anti-lock electronic control module ground:
• Disconnect battery to starter relay cable.
• Remove harness connector C277 from anti-lock electronic control module.
• Set ohmmeter on the 200 ohm scale.
• Check for resistance between anti-lock electronic control module harness connector C277, Pin 4 and chassis ground.

C4 REAR ABS WARNING LIGHT POWER

• Check for voltage to REAR ABS warning light:
• Set multimeter on 20 VDC scale position.
• Key to RUN.
• Check voltage between harness connector C277, Pin 7 and a known good chassis ground.

C5 POWER TO REAR ABS WARNING LIGHT FUSE

• Check for voltage to fuse.
• Set multimeter to 20 VDC scale.
• Key to RUN.
• Check voltage between panel fuse connector and known good chassis ground.

C6 REAR ABS WARNING LIGHT BULB

• Check REAR ABS warning light bulb.

PINPOINT TEST D: YELLOW REAR ABS WARNING LIGHT SELF CHECK OK, BUT LIGHT AUTOMATICALLY BEGINS FLASHING

Description

The yellow rear ABS warning light will automatically begin a flash-out sequence if the diagnostic line Circuit 571 (BK/O) or 483 (R) is shorted to ground. This will result in a blown fuse for the Keep-Alive Memory power for the anti-lock electronic control module. An open Keep-Alive Memory (KAM) fuse is most likely caused by a grounded diagnostic connector.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Intermittent anti-lock electronic control module power circuit
• Intermittent anti-lock electronic control module ground circuit
• Intermittent rear ABS warning light circuit
• Blown Keep-Alive Memory fuse

D1 OBSERVE REAR ABS WARNING LIGHT FOR FLASH SEQUENCE

• Observe REAR ABS warning light and determine if the flashing is a diagnostic trouble code (one or more short pulses followed by one long pulse).

D2 INTERMITTENT POWER TO ANTI-LOCK ELECTRONIC CONTROL MODULE

• Remove the harness connector C277 from the anti-lock electronic control module.
• Set multimeter to 20 VDC scale.
• Key to RUN.
• Shake the instrument panel harness while measuring battery voltage between Pin 1, Pin 9 and chassis ground.

D3 DAMAGED ANTI-LOCK ELECTRONIC CONTROL MODULE GROUND

• Disconnect the battery ground cable.
• Set the multimeter on the 200 ohm scale.
• Shake the anti-lock electronic control module harness while reading the resistance between Pin 4 and chassis ground.

The yellow RABS warning light should automatically begin a flash-out sequence if the diagnostic connector is shorted to ground for at least one second. This flashout sequence can be observed by watching the yellow REAR ABS warning light. There are a few conditions that will prevent the flashout from occurring. These must be resolved before continuing the service.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Burned-out brake rear lights
• Missing anti-lock electronic control module power (Circuit 601 [LB/PK] and associated fuse)
• Shorted yellow rear ABS warning light circuit (Circuit 603 [DG])
• Incorrect anti-lock electronic control module (RABS I vs. RABS II)

 CAUTION: RABS I vehicles that have been upgraded with RABS II anti-lock electronic control module will not have Keep-Alive Memory and will not be able to store codes when the vehicle is turned off.

NOTE: A RABS I system that has previously been serviced might have had its anti-lock electronic control module upgraded to a RABS II. In the event that you are uncertain whether you have a RABS I or RABS II anti-lock electronic control module, check the anti-lock electronic control module part number to be certain of the type of system you have.

• Part number F3TF-2C018: RABS II anti-lock electronic control module
• Part number F3UF-2C018: RABS II anti-lock electronic control module
• All other part numbers are RABS I anti-lock electronic control module

PINPOINT TEST E: YELLOW REAR ABS WARNING LIGHT SELF CHECK OK, BUT NO DIAGNOSTIC TROUBLE CODE WHEN DIAGNOSTICS ARE STARTED

E1 DETERMINE IF SYSTEM IS RABS I OR RABS II

• Determine if the ABS system is a RABS I or a RABS II system.

E2 CHECK FOR BURNED-OUT REAR BRAKE LIGHTS

• Press on brake pedal while observing rear brake lights.

E3 CHECK FOR LOSS OF BRAKE INPUT TO ANTI-LOCK ELECTRONIC CONTROL MODULE

• Remove the harness connector C277 from the anti-lock electronic control module. Check for terminal backout.
• Set multimeter to 20 VDC range.
• Press on brake pedal hard enough to turn on rear brake lights.
• Measure voltage from harness connector C277, Pin 11 to chassis ground while brake pedal is pressed.

E4 CHECK POWER TO THE ANTI-LOCK ELECTRONIC CONTROL MODULE

• Key to RUN.
• Measure the voltage between RABS harness connector C277, Pin 1 (or Pin 9) and chassis ground.

E5 CHECK FOR SHORTS IN ANTI-LOCK ELECTRONIC CONTROL MODULE HARNESS CONNECTOR

• With same setup as in Step E4, observe REAR ABS warning light.

E6 CHECK CIRCUIT 571 (BK/O) CONTINUITY

• Set the multimeter to the 200 ohm scale.
• Disconnect the RABS diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Measure resistance of Circuit 571 (BK/O) from diagnostic connector C159 to anti-lock electronic control module harness connector C277, Pin 12.

PINPOINT TEST F: OPEN RABS II ISOLATION SOLENOID CIRCUIT (DTC 2)

Description

Code 2 is generated when the anti-lock electronic control module detects an open circuit in Circuit 599 (PK/LG). The code can also be generated by a failed isolation solenoid (open coil) internal to the RABS valve or a failed internal anti-lock electronic control module circuit.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Terminal backout in the anti-lock electronic control module harness connector at Pin 13
• Terminal backout in the RABS valve harness connector at Pin 1
• Bulkhead connector (between engine compartment and instrument panel) terminal backout or loose connection
• Anti-lock electronic control module or RABS valve connectors not fully mated with component
• Intermittent open in Circuit 599 (PK/LG)

F1 CHECK YELLOW RABS WARNING LAMP

• Key off.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Reconnect diagnostic connector C159.
• Key on.

F2 VERIFY INTEGRITY OF ANTI-LOCK ELECTRONIC CONTROL MODULE HARNESS CONNECTION

• Key off.
• Disconnect battery ground cable.
• Remove the anti-lock electronic control module harness connector C277.
• Inspect module Pin 13.
• Pull gently on Pin 13 (PK/LG) wire just behind the harness connector C277.

F3 VERIFY INTEGRITY OF RABS VALVE CONNECTION

• Remove RABS valve connector C158.
• Inspect RABS valve component connector C158 for contamination or loose terminals.
• Pull gently on Pin 1 (PK/LG) just behind the harness connector C158.

F4 CHECK FOR CONTINUITY ALONG HARNESS CIRCUIT 599 (PK/LG)

• Verify multimeter is on 200 ohm scale.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 13 (PK/LG) and RABS valve component side connector harness connector C158, Pin 1.

F5 CHECK FOR OPEN RABS VALVE ISOLATION SOLENOID

• Verify multimeter is on 200 ohm scale.
• Measure resistance between RABS valve component side connector Pins 1 (PK/LG) and 3 (BK/W).

F6 CLEAR CODE/PULL CODE

• Key off.
• Reconnect battery ground cable.
• Verify all connectors are installed.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Key to RUN.
• Begin diagnostic trouble code flashout by connecting Circuit 571 (BK/O) to a chassis ground for at least 1 second.

PINPOINT TEST G: OPEN RABS II DUMP SOLENOID CIRCUIT (DTC 3)

Description

Code 3 is generated when the anti-lock electronic control module detects an open in Circuit 664 (Y/LG) or 274 (BK/W). The code can also be generated by a failed dump solenoid (open coil) internal to the RABS valve or a failed internal anti-lock electronic control module circuit.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Terminal backout in the anti-lock electronic control module harness connector at Pin 8 or 14
• Terminal backout in the RABS valve harness connector at Pin 2
• Bulkhead connector (between engine compartment and instrument panel) terminal backout or loose connection
• Anti-lock electronic control module or RABS valve connectors not fully mated with component
• Intermittent open in Circuit 664 (Y/LG)

G1 CHECK YELLOW RABS WARNING LAMP

• Key off.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Reconnect diagnostic connector C159.
• Key on.

G2 VERIFY INTEGRITY OF ANTI-LOCK ELECTRONIC CONTROL MODULE CONNECTION

• Key off.
• Disconnect battery ground cable.
• Remove the anti-lock electronic control module connector C277.
• Inspect anti-lock electronic control module Pins 8 and 14.
• Pull gently on each wire just behind Pins 8 and 14 on harness connector C277.

G3 VERIFY INTEGRITY OF RABS VALVE CONNECTION

• Remove RABS valve connector C158.
• Inspect RABS valve connector C158, Pin 2.
• Gently pull on Pin 2 wire just behind RABS harness connector C277.

G4 CHECK FOR CONTINUITY ALONG HARNESS CIRCUIT 664 (Y/LG) FROM ANTI-LOCK ELECTRONIC CONTROL MODULE CONNECTOR C277, PINS 8 AND 14

• Set multimeter on 200 ohm scale.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 8 and RABS valve harness connector C158, Pin 2.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 14 and RABS valve harness connector C158, Pin 2.

G5 CHECK FOR OPEN RABS DUMP VALVE SOLENOID

• Verify multimeter is on 200 ohm scale.
• Measure resistance between RABS valve Pins 2 and 3.

G6 CLEAR CODE/PULL CODE

• Turn key to OFF.
• Reconnect battery ground cable.
• Verify all connectors are installed.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Key to ON.
• Begin diagnostic trouble code flashout by connecting Circuit 571 (BK/O) to a chassis ground for at least 1 second.

PINPOINT TEST H: OPEN/GROUNDED RABS II VALVE RESET CIRCUIT (DTC 4)

Description

Code 4 is generated when the anti-lock electronic control module detects a short (less than 10 k ohms) in Circuit 535 (LB/R). This can indicate a short or open in the valve reset switch circuit or a hydraulic leak into dump section of the RABS valve.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Terminal backout in the anti-lock electronic control module harness connector at Pin 6
• Terminal backout in the RABS valve harness connector at Pins 4 or 3
• Bulkhead connector (between engine compartment and instrument panel) terminal backout or loose connection
• Anti-lock electronic control module or RABS valve connectors not fully mated with component
• Open or intermittent open in Circuit 535 (LB/R) or Circuit 274 (BK/W)
• Short or intermittent short in Circuit 535 (LB/R)
• Defective RABS valve
• Worn or damaged anti-lock electronic control module

H1 CHECK WARNING LIGHTS

• Key off.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Reconnect diagnostic connector C159.
• Key on.

H2 VERIFY INTEGRITY OF ANTI-LOCK ELECTRONIC CONTROL MODULE CONNECTION

• Key to off.
• Disconnect battery ground cable.
• Inspect anti-lock electronic control module component connector C277, Pin 6.
• Inspect anti-lock electronic control module harness connector C277, Pin 6.
• Pull gently on Pin 6 wire just behind the anti-lock electronic control module harness connector C277.

H3 VERIFY INTEGRITY OF RABS VALVE CONNECTION

• Remove RABS valve connector C158.
• Inspect RABS valve component connector C158, Pins 4 and 3.
• Inspect RABS valve harness connector C158, Pins 4 and 3.
• Pull gently on Pin 4 wire just behind the RABS valve harness connector C158.
• Pull gently on Pin 3 just behind the RABS valve harness connector C158.

H4 CHECK FOR CONTINUITY ALONG ANTI-LOCK ELECTRONIC CONTROL MODULE HARNESS CIRCUIT 535 (LB/R)

• Set multimeter on 200 ohm scale.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 6 and RABS valve harness connector C158, Pin 4.

H5 CHECK FOR CONTINUITY ALONG GROUND CIRCUIT 274 (BK/W)

• Set multimeter on 200 ohm scale.
• Measure resistance between RABS valve harness connector C158, Pin 3 and negative battery post.

H6 CHECK FOR SHORT ALONG ANTI-LOCK ELECTRONIC CONTROL MODULE HARNESS CIRCUIT 535 (LB/R)

• Set multimeter on 200 ohm scale.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 6 and chassis ground.

H7 CHECK FOR CLOSED RABS VALVE RESET SWITCH

• Verify multimeter is on 200 k ohm scale.
• Measure resistance between RABS valve connector C158, Pin 4 and RABS valve body.

H8 CHECK RESISTANCE BETWEEN VALVE SWITCH AND VALVE COMMON

• Verify multimeter is on 200 k ohm scale.
• Measure resistance between RABS valve Pins 4 and 3.

H9 CLEAR CODE/PULL CODE

• Key off.
• Reconnect battery ground cable.
• Verify all connectors are installed.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Key to RUN. Begin diagnostic trouble code flashout by connecting Circuit 571 (BK/O) to a chassis ground for at least 1 second.

H10 VERIFY PROPER WARNING LIGHT PROVEOUT

• Start the vehicle and observe the REAR ABS warning light for proper warning light proveout.

H11 VALVE RESET SWITCH CHECK

• Drive the vehicle at approximately 16 km/h (10 mph) on dry pavement.

 CAUTION: Do not exceed 16 km/h (10 mph) to prevent flat-spotting of tires.

• Press on brake pedal hard enough to lock all four wheels.
• After the vehicle has stopped, place the vehicle in NEUTRAL or PARK and take foot off the brake pedal.
• Wait 30 seconds.

H12 RABS HYDRAULIC VALVE LEAK TEST

NOTE: The condition is similar to the master cylinder bypass condition. It is important that the brake pedal be quickly and forcefully applied to rule out master cylinder bypass as the cause if a hydraulic leak is detected. Typically, master cylinder bypass occurs only at low line pressures.

• Press hard on the brake pedal and keep pressure on the brake pedal for 30 seconds.
• While keeping pressure on the brake, monitor the height of the brake pedal.

H13 OBTAIN DIAGNOSTIC TROUBLE CODE

• Obtain diagnostic trouble code.

H14 BLOCKED ISOLATION ORIFICE

• Disconnect anti-lock electronic control module harness connector C277.
• Raise the vehicle on a hoist far enough to allow all wheels to spin freely.
• Verify that the vehicle is in 4x2 mode and the hubs are unlocked (4x4 only).
• Start the vehicle and allow rear wheels to spin at idle for at least 30 seconds.
• Apply the brake pedal with the force of a normal traffic stop.

PINPOINT TEST J: EXCESSIVE DUMP SOLENOID ACTIVITY (DTC 5)

Description

Code 5 is generated when the maximum number of allowable dump pulses has been exceeded. The system will only recognize this condition during an anti-lock stop in 2WD mode. The code can be caused by a blocked RABS dump valve orifice, a stuck dump valve, an open circuit in Circuit 210 (LB), a worn or damaged 4x4 transfer case that causes the vehicle to remain in 4x4 after 4x2 has been selected, or mechanical problems in the rear brake system (rear brakes might lock).

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Parking brake drag
• Worn or damaged 4x4 switch
• Rear brake assembly grabby or hanging up
• Connector corrosion or contamination
• Intermittent open in Circuit 210 (LB)
• Pierced wire insulation to battery power (4x4 only)

J1 CHECK YELLOW RABS WARNING LAMP

• Key off.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Reconnect diagnostic connector C159.
• Key on.

J2 DRIVE STATUS

J3 CHECK FOR INCORRECT 4WD SWITCH SIGNAL, OR SHORT TO POWER TO ANTI-LOCK ELECTRONIC CONTROL MODULE

• Disconnect anti-lock electronic control module harness connector C277 to deactivate RABS.
• Key to RUN.
• Shift into 4x4 mode.
• Set multimeter to 20 VDC scale.
• Measure voltage between Pin 5 of the anti-lock electronic control module harness connector C277 and chassis ground.

J4 CHECK FOR LOW OR ERRATIC RABS SENSOR SIGNAL

• Disconnect anti-lock electronic control module harness connector C277.
• Position vehicle on hoist and raise both front and rear wheels just enough to clear the floor.
• Start the engine and turn the wheels at 8 km/h (5 mph).
• Place multimeter on 2000 mVAC scale.
• Measure the voltage across anti-lock electronic control module harness connector C277, Pins 3 and 10.

J5 CLEAR CODE/PULL CODE

• Key off.
• Reconnect battery ground cable.
• Verify all connectors are installed.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Key on.
• Begin diagnostic trouble code flashout by connecting Circuit 571 (BK/O) to a chassis ground for at least 1 second.

J6 VERIFY PROPER WARNING LIGHT PROVEOUT

• Start the vehicle and observe the REAR ABS warning light for proper warning light proveout.

J7 BASE BRAKE STOPPING TEST

• Remove the harness connector C277 from the anti-lock electronic control module.
• Drive the vehicle at approximately 32 km/h (20 mph).
• Perform a light to medium (normal traffic) stop.

J8 DRY ROAD STOP TEST

• Drive the vehicle at approximately 16 km/h (10 mph) on dry pavement.

 CAUTION: Do not exceed 16 km/h (10 mph) to prevent flat-spotting of tires.

• Press on brake pedal hard enough to lock all four wheels and observe the left rear wheel in the driver side mirror.

J9 VERIFY PROPER RABS II OPERATION IN 4X2

 WARNING: PERFORM THIS TEST ON AN AXLE HOIST ONLY.

NOTE: Because vehicle is not on the ground, wheels will spin for a significant time. This is not indicative of vehicle braking performance.

• Place vehicle on the hoist and raise high enough to clear all wheels off the ground.
• Verify vehicle is in 4x2 mode (4x4 vehicles only.)
• Place vehicle transmission in Drive Low (automatic) or 1st gear (manual).
• Accelerate engine so that speedometer indicates 16 km/h (10 mph).
• Press hard on the brake pedal until wheels stop.

J10 OBTAIN DIAGNOSTIC TROUBLE CODE

• Obtain diagnostic trouble code.

PINPOINT TEST K: ERRATIC SPEED SENSOR CIRCUIT (DTC 6)

Description

Code 6 is generated when the anti-lock electronic control module detects an interruption in the continuous signal from the RABS sensor while rolling, caused by an intermittent open internal to the RABS sensor, Circuit 519 (LG/BK), Circuit 523 (R/PK), or a damaged RABS sensor ring. This condition can be detected any time the brake pedal is not applied and 20 seconds has elapsed since the ignition self test.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Terminal backout in the anti-lock electronic control module harness connector at Pins 3 and 10
• Terminal backout in the RABS sensor harness connector at Pins A and B
• Bulkhead connector (between engine compartment and instrument panel) terminal backout or loose connection
• Anti-lock electronic control module or RABS sensor connectors are not fully mated with component
• Intermittent open/short in Circuit 519 (LG/BK) or Circuit 523 (R/PK)
• Damaged RABS sensor (possibly metal shavings on pole piece)
• Damaged RABS sensor ring (possibly teeth missing)

K1 CHECK YELLOW RABS WARNING LAMP

• Key off.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Reconnect diagnostic connector C159.
• Key to RUN.

K2 VERIFY INTEGRITY OF ANTI-LOCK ELECTRONIC CONTROL MODULE HARNESS CONNECTION

• Key off.
• Disconnect battery ground cable.
• Remove the anti-lock electronic control module connector C277.
• Inspect anti-lock electronic control module connector C277 for contamination and loose or bent terminals.
• Pull gently on Circuit 519 (LG/BK) just behind Pin 3 on the harness connector C277.
• Pull gently on Circuit 523 (R/PK) just behind Pin 10 on the harness connector C277.

K3 VERIFY INTEGRITY OF RABS SENSOR CONNECTION

• Verify key is off.
• Remove RABS sensor harness connector C404.
• Inspect RABS connector C404 for contamination and bent or loose terminals.
• Gently pull on Circuit 519 (LG/BK) behind Pin B of harness connector C404.
• Gently pull on Circuit 523 (R/PK) behind Pin A of harness connector C404.

K4 VERIFY PROPER RABS SENSOR WIRE ROUTING

• Inspect wire routing.

K5 VERIFY RABS SENSOR INTEGRITY

• Check resistance between Pins A and B of the RABS sensor component connector.

K6 CHECK FOR ERRATIC RABS SENSOR SIGNAL AND LOOSE WIRE CONNECTORS

• Set multimeter on the 20 k ohm scale.
• Check resistance between Pin 10 and Pin 3 of the harness connector C277 while shaking the harness from RABS sensor to anti-lock electronic control module.

K7 CHECK FOR METAL CHIPS ON RABS SENSOR MAGNET POLE PIECE

• Verify key is off.
• Remove the RABS sensor from the rear axle housing and inspect for a buildup of metal chips on RABS sensor magnetic pole.

K8 CLEAR CODE/PULL CODE

• Key off.
• Reconnect battery ground cable.
• Verify all connectors are installed.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Key to ON.
• Begin diagnostic trouble code flashout by connecting Circuit 571 (BK/O) to a chassis ground for at least 1 second.

K9 VERIFY PROPER WARNING LIGHT PROVEOUT

• Key on and observe the REAR ABS warning light for proper bulb proveout.

K10 MEASURE RABS SENSOR OUTPUT

• Put vehicle on hoist and raise so that the rear wheels can rotate freely.
• Verify the vehicle is in 4x2 mode and hubs are unlocked.
• Set an AC voltmeter on the 2000 mV scale.
• Remove the cap from the RABS sensor test connector C143 and connect the AC voltmeter across the connector leads.
• Start the engine and turn the rear wheels at 8 km/h (5 mph).
• Measure the voltage output of the RABS sensor.

K11 MEASURE RABS SENSOR AIR GAP

• Remove rear axle differential cover.
• Measure the shortest distance from the RABS sensor pole piece to the teeth on the RABS sensor ring.
• Rotate the axle 60-90 degrees.
• Repeat the two previous steps (measure and rotate) five times for a total of five measurements.

K12 IMPROPER RABS SENSOR GAP RESOLUTION

• Verify that the installed RABS sensor is seated fully in the bore and the hold-down bolt is tightened to specification.
• Repeat measurements from Step K11.

K13 CHECK CONDITION OF RABS SENSOR RING TEETH

• Carefully inspect each tooth on the RABS sensor ring. (Rear axle differential cover should still be off.)

PINPOINT TEST L: NO ISOLATION SOLENOID DURING SELF CHECK (DTC 7)

Description

Code 7 is generated when the anti-lock electronic control module detects a missing isolation solenoid output. This can only be detected during an ignition self check or during RABS stop.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Anti-lock electronic control module internal fuse blown or internal open circuit
• Shorted isolation solenoid internal to the RABS valve
• Short or intermittent short in Circuit 599 (PK/LG)
• Contamination or bent Pins 1 and 3 of RABS valve connector shorting together

L1 CHECK YELLOW RABS WARNING LAMP

• Key off.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Reconnect diagnostic connector C159.
• Key to RUN.

L2 CHECK FOR RABS VALVE ISOLATION SOLENOID OR WIRING SHORTED TO GROUND

• Key off.
• Disconnect battery ground cable.
• Remove the anti-lock electronic control module harness connector C277.
• Set the multimeter on the 200 ohm scale.
• Measure the resistance between anti-lock electronic control module harness connector C277, Pin 13 and chassis ground.

L3 CHECK INTEGRITY OF RABS VALVE CONNECTION

• Remove RABS valve connector C158.
• Inspect RABS valve connector C158 and Pins 1 and 3.

L4 CHECK FOR SHORTED RABS VALVE ISOLATION SOLENOID

• Verify RABS valve harness connector C158 removed.
• Set the multimeter on the 200 ohm scale.
• Measure the resistance between Pins 1 and 3 of RABS valve.

L5 CHECK FOR SHORT TO GROUND ALONG HARNESS CIRCUIT 599 (PK/LG)

• Set multimeter on 20 k ohm scale.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 13 (PK/LG) and chassis ground.

L6 CLEAR CODE/PULL CODE

• Key off.
• Reconnect battery ground cable.
• Verify all connectors are installed.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Key to RUN.
• Begin diagnostic trouble code flashout by connecting Circuit 571 (BK/O) to a chassis ground for at least 1 second.

PINPOINT TEST M: NO DUMP SOLENOID DURING SELF CHECK (DTC 8)

Description

Code 8 is generated when the anti-lock electronic control module detects a missing dump solenoid output. This concern can only be detected during an ignition self test or during a REAR ABS stop.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Anti-lock electronic control unit internal fuse blown or internal open circuit
• Shorted dump solenoid internal to RABS valve
• Short or intermittent short in Circuit 664 (Y/LG)
• Bulkhead connector between engine compartment and instrument panel terminals shorted

M1 CHECK YELLOW RABS WARNING LAMP

• Key off.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Reconnect diagnostic connector C159.
• Key to RUN.

M2 CHECK FOR RABS VALVE DUMP SOLENOID OR WIRING SHORTED TO GROUND

• Key off.
• Disconnect battery ground cable.
• Remove the anti-lock electronic control module harness connector C277.
• Set the multimeter on the 200 ohm scale.
• Measure the resistance between anti-lock electronic control module harness connector C277, Pin 8 and chassis ground.
• Measure the resistance between anti-lock electronic control module harness connector C277, Pin 14 and chassis ground.

M3 CHECK FOR SHORTED RABS VALVE DUMP SOLENOID

• Remove RABS valve harness connector C158.
• Set the multimeter on the 200 ohm scale.
• Measure the resistance between Pins 3 and 2 of RABS valve.

M4 CHECK FOR SHORT TO GROUND ALONG HARNESS CIRCUIT 664 (Y/LG)

• Set multimeter on 20 ohm scale.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 8 and RABS valve harness connector C158, Pin 2.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 14 and valve harness connector C158, Pin 2.

M5 CLEAR CODE/PULL CODE

• Key off.
• Reconnect battery ground cable.
• Verify all connectors are installed.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Key to RUN.
• Begin diagnostic trouble code flashout by connecting Circuit 571 (BK/O) to a chassis ground for at least 1 second.

PINPOINT TEST N: HIGH SPEED SENSOR RESISTANCE (DTC 9)

Description

Code 9 is generated when the anti-lock electronic control module detects high RABS sensor resistance. The anti-lock electronic control module will consider the RABS sensor circuit to have a high resistance when it exceeds approximately 3 k ohms. The code can also be generated by a failed internal anti-lock electronic control module circuit.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Terminal backout in the anti-lock electronic control module harness connector at Pin 3 or Pin 10
• Terminal backout in the RABS sensor harness connector at Pins A or B
• Anti-lock electronic control module or RABS sensor connectors not fully mated with component
• Open or intermittent open in Circuit 519 (LG/BK) or Circuit 523 (R/PK)

N1 CHECK YELLOW RABS WARNING LAMP

• Key off.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Reconnect diagnostic connector C159.
• Key on.

N2 VERIFY INTEGRITY OF ANTI-LOCK ELECTRONIC CONTROL MODULE CONNECTION

• Key off.
• Disconnect battery ground cable.
• Remove the anti-lock electronic control module harness connector C277.
• Pull gently on Circuit 519 (LG/BK) just behind Pin 3 on the anti-lock electronic control module harness connector C277.
• Pull gently on Circuit 523 (R/PK) just behind Pin 10 on the anti-lock electronic control module harness connector C277.

N3 VERIFY INTEGRITY OF RABS SENSOR CONNECTION

• Remove RABS sensor harness connector C404.
• Inspect RABS sensor component connector C404 for contamination or loose terminals.
• Gently pull on Circuit 519 (LG/BK) behind Pin B of harness connector C404.
• Gently pull on Circuit 523 (R/PK) behind Pin A of harness connector C404.

N4 CHECK FOR CONTINUITY ALONG HARNESS CIRCUITS 519 (LG/BK) and 523 (R/PK)

• Set multimeter on 200 ohm scale.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 3 and RABS sensor harness connector C404, Pin B.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 10 and RABS sensor harness connector C404, Pin A.

N5 CHECK FOR OPEN RABS SENSOR

• Measure resistance between RABS sensor Pins A and B.

N6 CLEAR CODE/PULL CODE

• Key off.
• Reconnect battery ground cable.
• Verify all connectors are installed.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Key to RUN.
• Begin diagnostic trouble code flashout by connecting Circuit 571 (BK/O) to a chassis ground for at least 1 second.

PINPOINT TEST P: LOW SPEED SENSOR RESISTANCE (DTC 10)

Description

Code 10 is generated when the anti-lock electronic control module detects low RABS sensor resistance. The code can also be generated by a short in Circuit 519 (LG/BK) or Circuit 523 (R/PK), or a failed internal anti-lock electronic control module circuit.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Short between anti-lock electronic control module harness connector Pin 3 and Pin 10
• Short between RABS sensor connector Pins A and B
• Bulkhead connector (between engine compartment and instrument panel) sensor terminals shorted together
• Intermittent short in Circuit 519 (LG/BK) or Circuit 523 (R/PK)

P1 CHECK YELLOW RABS WARNING LAMP

• Key off.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Reconnect diagnostic connector C159.
• Key on.

P2 VERIFY INTEGRITY OF ANTI-LOCK ELECTRONIC CONTROL MODULE CONNECTION

• Key off.
• Disconnect battery ground cable.
• Remove the anti-lock electronic control module harness connector C277.
• Pull gently on wire just behind Pin 3 on the harness connector C277.
• Pull gently on wire just behind Pin 10 on the harness connector C277.

P3 VERIFY INTEGRITY OF RABS SENSOR CONNECTION

• Remove RABS sensor harness connector C404.
• Inspect RABS sensor component connector C404.
• Gently pull on wire behind Pins A and B of harness connector C404.
• Gently pull on wire behind Pins A and B of component connector C404.

P4 CHECK FOR SHORT ALONG HARNESS CIRCUIT 519 (LG/BK) WITH CIRCUIT 523 (R/PK)

• Set multimeter on 20 k ohm scale.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 3 and Pin 10.

P5 CHECK FOR SHORT TO CHASSIS GROUND ALONG CIRCUIT 523 (R/PK)

• Verify multimeter is on 20 k ohm scale.
• Measure resistance between anti-lock electronic control module harness connector C277, Pin 10 and chassis ground.

P6 CHECK FOR SHORTED RABS SENSOR

• Measure resistance between RABS sensor Pins A and B.

P7 CLEAR CODE/PULL CODE

• Key off.
• Reconnect battery ground cable.
• Verify all connectors are installed.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Key to run.
• Begin diagnostic trouble code flashout by connecting Circuit 571 (BK/O) to a chassis ground for at least 1 second.

PINPOINT TEST Q: STOPLAMP CIRCUIT ALWAYS CLOSED (DTC 11)

Description

Code 11 is caused by the stoplight switch always being closed prior to the vehicle moving. If the stoplight switch remains closed when the vehicle begins to move, the REAR ABS warning light will turn on at approximately 26 km/h (16 mph). Code 11 will not be latched in the control anti-lock electronic control module's memory until the speed of the vehicle exceeds 60 km/h (37 mph) for at least 10 seconds. If the vehicle does not exceed 60 km/h (37 mph) for at least 10 seconds, then the REAR ABS warning light will turn on but the anti-lock electronic control module will not latch a code. Code 11 can be caused by a driver resting his foot on the brake pedal with just enough pressure to close the stoplight switch, while driving at least 60 km/h (37 mph) for a minimum of ten seconds. When this occurs, a Code 11 will be latched by the anti-lock electronic control module.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Terminal backout in the anti-lock electronic control module harness connector at Pin 11
• Missing (burned-out) stoplamps. All stoplamps must be missing or burned out to cause a Code 11
• An intermittent/continuous open in Circuit 511 (LG). This open would be between anti-lock electronic control module connector Pin 11 and the stoplight switch
• Worn or damaged stoplight switch

Q1 CHECK YELLOW RABS WARNING LAMP

• Key off.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Reconnect diagnostic connector C159.
• Key on.

Q2 CHECK VEHICLE STOPLAMP OPERATION

• Key off.
• Apply pressure to the brake pedal and then release pressure while observing the stoplamps.

Q3 CHECK VEHICLE STOPLAMPS

• Check vehicle stoplamp bulbs.

NOTE: Both bulbs need to be burned out to cause a Code 11.

Q4 CHECK FOR BLOWN STOPLAMP FUSE

• Remove and visually inspect stoplamp fuse located in the fuse panel.

Q5 CHECK FOR CONTINUITY BETWEEN ANTI-LOCK ELECTRONIC CONTROL MODULE CONNECTOR PIN 11 AND THE STOPLAMP SWITCH

• Set multimeter on 20 volt scale.
• Step on brake pedal.
• Measure voltage between anti-lock electronic control module harness connector C277, Pin 11 and chassis ground.

Q6 CLEAR CODE/PULL CODE

• Key off.
• Reconnect battery ground cable.
• Verify all connectors are installed.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Key to RUN.
• Begin diagnostic trouble code flashout by connecting Circuit 571 (BK/O) to a chassis ground for at least 1 second.

PINPOINT TEST R: LOSS OF HYDRAULIC FLUID DURING ANTI-LOCK STOP (DTC 12)

Description

Code 12 is generated when the anti-lock electronic control module detects that the brake fluid level in the brake master cylinder reservoir is low for one or more seconds during an anti-lock stop. It can also be generated by a short in the red brake warning lamp circuit.

Possible Contributing Base Brake Component/Vehicle Wiring Concerns

• Low brake master cylinder reservoir fill level
• Fluid leaks in vehicle brake system
• Worn or damaged fluid level switch, or fluid level switch circuit shorted to ground
• Brake master cylinder reservoir float that sticks in the bottom of brake master cylinder reservoir or does not float
• Damaged diode/resistor element in red brake warning lamp circuit
• Damaged ignition switch
• Ground short or open in Circuit 512 (T/LG) or Circuit 531 (DG/Y)
• Damaged anti-lock electronic control module

R1 CHECK WARNING LIGHTS

• Key off.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Reconnect diagnostic connector C159.
• Key on.

R2 CHECK BRAKE FLUID LEVEL IN MASTER CYLINDER

• Key off.
• Check the brake fluid level in the brake master cylinder reservoir.

R3 VERIFY FLOAT BUOYANCY

• Remove the brake master cylinder reservoir filler cap.
• Attempt to push down the float with a clean, blunt steel implement, then let it float back up.

R4 CHECK CIRCUIT 531 (DG/Y) FOR GROUND SHORT

• Key off.
• Disconnect brake fluid level switch harness connector C170.
• Disengage parking brake.
• Check for ground short on Circuit 531 (DG/Y) at brake fluid level switch harness connector C170.

R5 CHECK DIODE/RESISTOR ELEMENT

• Engage parking brake.
• Check for ground short on Circuit 531 (DG/Y) at brake fluid level switch harness connector C170.

R6 CHECK CIRCUIT 512 FOR GROUND SHORT

• Key off.
• Disconnect battery negative cable.
• Disconnect fluid level switch.
• Disconnect ignition switch.
• Disconnect anti-lock electronic control module.
• Check for short to ground on Pin 2 of anti-lock electronic control module harness connector C277 (Circuit 512 [T/LG]).

R7 CHECK IGNITION SWITCH

• Reconnect ignition switch.
• Check for short to ground on Pin 2 of anti-lock electronic control module harness connector C277 (Circuit 512 [T/LG]).

R8 CHECK BRAKE FLUID LEVEL SWITCH

• Reconnect brake fluid level switch connector C170.
• Check for short to ground on Pin 2 of anti-lock electronic control module harness connector C277 (Circuit 512).

R9 CLEAR CODE/PULL CODE

• Key off.
• Reconnect battery negative cable.
• Verify all connectors are installed.
• Locate and disconnect the diagnostic connector C159 from its mating half (Circuits 571 [BK/O] and 483 [R]).
• Key to run.
• Begin diagnostic trouble code flashout by grounding Circuit 571 (BK/O) for 1 second.

PINPOINT TEST S: VERIFICATION DRIVE TEST

Purpose

This drive test will be used when either of the two conditions listed below exists.

1. Required Service Verification
• This drive procedure will be used after all vehicle service. Once a vehicle has been serviced, it is necessary to verify the service by driving the vehicle. This is because the anti-lock electronic control module is unable to detect some system concerns until the vehicle is being driven a certain way. Therefore the drive verification test is a very important step.
2. Symptom Evaluation Drive
• When a vehicle is brought to the dealer, the customer might have only a general concern about the way his or her vehicle is braking. In these situations there might not be a clear system concern to troubleshoot. In this type of situation, this drive test is designed to produce common system concern symptoms. Use this drive test to determine a symptom. Once a symptom is found, a symptom troubleshooting procedure can be followed to service the vehicle.

Drive Description

This drive test is designed to be a generic drive test that is used for the three purposes listed below:

• to verify service of the RABS II system on a vehicle
• to attempt to recreate an intermittent concern
• to attempt to detect a symptom when a diagnostic trouble code or a concern symptom is not known

S1 KEEP ALIVE MEMORY (KAM) FUSE CHECK

• Key to RUN. Observe REAR ABS warning light proveout.
• With the headlamps on and while pushing on the brake pedal, monitor the yellow REAR ABS warning light in the dash for 10 seconds.

S2 PERFORM LOW SPEED STOP

NOTE: Wetting down the area where stop is to be performed will aid this test.

NOTE: An assistant to observe rear wheels is helpful.

• Drive vehicle at approximately 16 km/h (10 mph).
• Press on brake pedal hard enough to lock all four wheels, and observe the left rear wheel in the driver's mirror.
• Repeat the second step, except observe right rear wheel in passenger mirror.

S3 CHECK FOR UNWARRANTED RABS II ACTIVITY

NOTE: Stop should be performed on dry pavement.

• Drive vehicle at approximately 32 km/h (20 mph).
• Turn off the windshield wipers if they are on. (Wipers can cause a pulsation in the brake pedal that can be mistaken for RABS II activity.)
• Perform a light to medium (normal traffic) stop.
• Feel for pulsation in the brake pedal within 10 seconds after the vehicle has come to a stop.

S4 BRAKE STOPLAMP/SWITCH CHECK

• Key to RUN.
• Press on the brake pedal.
• Release brake pedal.

S5 DETERMINE DRIVE TEST IS COMPLETE

S6 DETERMINE NEXT DIAGNOSTIC STEP BASED ON BRAKE SYMPTOM

• Hard or soft brake pedal.
• Lack of sufficient vehicle deceleration upon brake application.

S7 OBTAIN DIAGNOSTIC TROUBLE CODE

• Obtain diagnostic trouble code.

PINPOINT TEST T: INTERMITTENT DIAGNOSIS

As previously mentioned, intermittent concerns are the most difficult to diagnose.

An understanding of code storage and automatic code erasure is important.

First, codes can only be stored if the anti-lock electronic control module has power. The anti-lock electronic control module gets primary power from the ignition feed into Pins 1 and 9. If this voltage is missing or less than 11 V, the anti-lock electronic control module will not initialize and therefore, a code cannot be stored. However, any code already in memory will be retained as long as the Keep-Alive Memory power is available. Code 16 (system OK) is present whenever the anti-lock electronic control module sees the required voltage (assuming no other diagnostic trouble codes are present).

Therefore, some codes read out in the System Pre-Check might not result in any trouble found in the pinpoint test performed. More likely, this is an indication of an intermittent electrical concern.

At times, running completely through a pinpoint test will not lead to a concern resolution. Often, the concern is due to an intermittent connection, termination, or damaged circuit. An attempt has been made to point out obvious sources for potential intermittents within the pinpoint tests. However, it should be noted that several circuits pass through one or more connections between components. These are also areas of potential concern and should be considered.

T1 CLEAR CODES, RECONNECT COMPONENTS

• Reinstall any components removed and reconnect all connections.
• Clear all codes.
• Key to RUN.

T2 SERVICE CONNECTOR/TERMINAL FAULT

• Most likely problem is at one of the affected component connectors so that terminals unseat or back out upon installation. At each affected connection, look for:
• bent terminals.
• damaged connector terminal locks.
• damaged connector wedge.
• If one of the above conditions is found, check the length of the affected circuit once the connection is remade. If the wire is too tight (short), damage is likely to recur once vehicle is given back to the customer. Service the wire as necessary to correct tight wire conditions.

T3 WIGGLE TEST

• Leave key on.

NOTE: Start at one component and wiggle connector by connector until the whole circuit has been tested.

• Wiggle an affected circuit in one location only.
• Observe REAR ABS warning light.

T4 VERIFY ALL CIRCUITS HAVE BEEN TESTED

T5 RETRIEVE CODE

• Retrieve code.

T6 VERIFY ALL APPROPRIATE DIAGNOSTIC PROCEDURES HAVE BEEN RUN

NOTE: All steps of the pinpoint test for the code being serviced must be completed. (If some tests were performed, then go the pinpoint step last completed and continue.)

T7 VERIFY CONDITION RESOLVED

• Clear all codes.
• Key off.
• Retrieve code.

PINPOINT TEST U: REAR ABS AND SPEEDOMETER ARE NOT FUNCTIONING CORRECTLY

This procedure is intended to determine whether the cause for loss of or erratic Programmable Speedometer/Odometer Module (PSOM) function is due to the lack of a signal from the RABS Sensor.

There are two basic reasons that PSOM would not receive a signal from the RABS sensor:

1. The RABS sensor or the signal from the RABS sensor is faulty and is either not being generated or not reaching the anti-lock electronic control module or PSOM. In cases where the concern is not intermittent and not reaching the anti-lock electronic control module, the rear ABS warning light will be on upon vehicle start-up and a diagnostic trouble code should be obtained upon RABS II diagnostic trouble code retrieval. Where the concern is intermittent and the rear ABS warning light does not come on during vehicle start-up, a diagnostic trouble code can still be stored in the anti-lock electronic control module (see the Symptom Chart).
2. The wiring or interconnections in the vehicle harness between the anti-lock electronic control module and the PSOM are faulty. This can lead to erratic PSOM function and is difficult to diagnose.
• This procedure will only determine whether the RABS sensor is functioning based upon whether a signal is received at the PSOM. If it is determined that the RABS sensor is sending out a proper signal, refer to Section 13-01.

U1 DETERMINE STATE OF ABS WARNING LIGHT

• Observe rear ABS warning light.
• Key to START.
• Allow key to return to the RUN position.

U2 OBTAIN REAR ABS CODE

• Obtain rear ABS code (refer System Pre-Check).

NOTE: Any other code obtained represents a rear ABS system concern and does not have an effect on the ability of the RABS sensor to send the speed signal to PSOM. Resolve the rear ABS system concern indicated by the diagnostic trouble code first. When the rear ABS system concern is corrected, repeat this step to continue PSOM concern diagnosis.

U3 VERIFY RABS SENSOR SPEED SIGNAL AT ANTI-LOCK ELECTRONIC CONTROL MODULE

• Key off.
• Remove the harness connector C277 from the anti-lock electronic control module.
• Raise the vehicle so that all the wheels are clear of the ground. If the vehicle is a 4x4, verify the transfer case is in the 4x2 mode.
• Connect Rotunda 88 Digital Multimeter 105-00053 or equivalent between harness connector C277, Pin 10 (Circuit 523-R/PK) and Pin 3 (Circuit 519 — LG/BK).
• Set the meter to the frequency counter (Hz) setting.
• Gradually spin the rear wheels.