1996 Bronco/F-Series

Section 07-07: Transfer Case, 4x4 System, Service

1996 F-150, 250, 350 (4x4), and Bronco Vehicles with Manual Shift Transfer Case; All Bronco and F-150 4x4 Vehicles with Electronic Shift Transfer Case Only Workshop Manual

DIAGNOSIS AND TESTING

Pinpoint Tests

PINPOINT TEST A: POWER AND GROUNDS DIAGNOSIS

A1 BAD OR INTERMITTENT POWER TO CONTROL MODULE

Check for open or intermittent in the module harness connector (C1) Pin 8 (battery +):

Disconnect the module harness connector C1 from the module.
Set the voltmeter on the 20 VDC scale.
Key to RUN.
Check voltage between C1 Pin 8 and chassis ground. (If there is no voltage, shake the module harness. Recheck for intermittent voltage.)

Is voltage steady and greater than 9V?

Yes	No
GO to A2.	REPAIR break in the B+ line.

A2 FAULTY CONTROL MODULE GROUND

Check for an intermittent or poor module ground:

Disconnect the battery.
Set the ohmmeter on the 20 ohm scale.
Shake the module harness and check the resistance between connector C1 Pin 3 and chassis ground. Repeat for Pin 2 to chassis ground.

Is resistance steady and less than 1 ohm?

Yes	No
REPLACE control module.	REPAIR poor ground circuit(s) and RETEST system.

PINPOINT TEST B: 4WD INDICATOR LAMP DIAGNOSIS

B1 ELECTRONIC 4-WHEEL DRIVE LAMP NOT FUNCTIONING PROPERLY

Check for voltage at the module harness connector Pin 4:

Key off.
Back-probe the module harness connector C2 at Pin 5 with module connected.
Set voltmeter to the 20 VDC scale.
Check the voltage between Pin 5 of the control module and chassis ground with the ignition switch off.

Is voltage less than 3V?

Yes	No
GO to B2.	REPAIR short to B+ between control module (Pin 4) and the electronic 4-wheel drive warning lamp.

B2 ELECTRONIC 4-WHEEL DRIVE LAMP NOT FUNCTIONING

Check for voltage at the control module Pin 5:

Back-probe the module harness connector C2 Pin 5 with the controller module connected.
Set the voltmeter to the 20 VDC scale.
Key to RUN.
Check the voltage between the electronic shift control module Pin 5 and chassis ground.

Is voltage steady and greater than 9V?

Yes	No
GO to Pinpoint Test C.	REPLACE control module.

PINPOINT TEST C: BRAKE SWITCH INPUT DIAGNOSIS

C1 STOPLAMP OPERATION

Check for stoplamp operation:

Apply the service brakes and observe the rear stoplamps.

Are stoplamps operating with brake pedal depressed?

Yes	No
GO to C2.	REPAIR the stoplamp circuit and RETEST.

C2 BAD OR INTERMITTENT BRAKE SWITCH INPUT

Check for intermittent open in the control module brake switch circuit:

Disconnect the module harness connector C2 from the module.
Set the voltmeter on the 20 VDC scale.
Check the voltage between the module harness connector C2 Pin 5 Circuit 783 (GY) and chassis ground while the brake pedal is depressed.
Shake module harness. Recheck for intermittent voltage.

Is voltage steady and greater than 9V?

Yes	No
REPLACE control module.	REPAIR break in the module to brake switch circuit.

PINPOINT TEST D: PARK/NEUTRAL POSITION SWITCH OR TRANSMISSION RANGE SENSOR DIAGNOSIS

D1 CONTROL MODULE PARK/NEUTRAL POSITION SWITCH TRANSMISSION RANGE SENSOR INPUT

Check for intermittent short in the module harness Connector C3 Pin 1:

Disconnect the module harness connector from the module.
Set the voltmeter on the 20 VDC scale.
Key to RUN.
With the transmission in NEUTRAL, check the voltage between Pin 5 and chassis ground.

Is voltage steady or intermittent and greater than 1V?

Yes	No
REPAIR short to voltage in Circuit 463 (R/W) or REPLACE Park/Neutral Position Switch.	GO to D2.

D2 FAULTY PARK/NEUTRAL POSITION SWITCH TRANSMISSION RANGE SENSOR OR CIRCUITRY

Check for short to ground in the module harness park/neutral position switch circuit:

Key off.
Disconnect module Connector C3 from the module.
Set ohmmeter to the 200 ohm scale.
With the transmission in DRIVE, check the resistance between the module harness connector Pin 1 and chassis ground.

Is resistance greater than 100 ohms?

Yes	No
GO to D3.	REPAIR short-to-ground or REPLACE park/neutral position switch or transmission range sensor.

D3 PARK/NEUTRAL POSITION SWITCH OR TRANSMISSION RANGE SENSOR OPEN

Check for open between module harness connector and park/neutral position switch:

Key off.
Disconnect module harness connector.
Set ohmmeter to the 200 ohm scale.
With the transmission in NEUTRAL, check the resistance between module harness Connector C3 Pin 1 and chassis ground.

Is resistance less than 50 ohms?

Yes	No
REPLACE electronic shift control module.	REPAIR open in park/neutral position switch circuit or REPLACE park/neutral position switch or transmission range sensor.

PINPOINT TEST E: TRANSFER CASE SPEED SENSORS DIAGNOSIS

E1 SPEED SENSOR POWER SUPPLY

Check for voltage at speed sensor positive (+) line:

Remove the transfer case harness connector from locating clip.
Set the voltmeter on the 20 VDC scale.
Key to RUN.
Back probe Pin 2 Circuit 774 (LG), check for voltage between the harness connector positive (+) pin and chassis ground.
Shake the connector and harness while checking the voltage.

Is voltage steady and greater than 4V?

Yes	No
GO to E2.	REPAIR open circuit. If fault still occurs REPLACE control module. REFER to the Electrical Schematics in this section.

E2 CONTINUITY TESTING OF THE SPEED SENSOR LINES

Check the continuity of the speed sensor signal and ground lines:

Key off.
Disconnect the module harness connector C3 from the module.
Remove the speed sensor connector from the speed sensor.
Set the ohmmeter to the 20 ohm scale.
Test the continuity of each wire from the speed sensor connector from their pins in the sensor harness connector to their corresponding pins in the connector C-3 Pins 2, 3.

Is resistance greater than 1 ohm?

Yes	No
REPAIR open circuit. REFER to the Electrical Schematics in this section.	GO to E3.

E3 SHORT-TO-GROUND TESTING OF SPEED SENSOR LINES

Check for short-to-ground or intermittent in the speed sensor signal circuit:

Key off.
Disconnect the module harness connector C3 from the module.
Disconnect the speed sensor connector from the speed sensor.
Set the ohmmeter on the 20 ohm scale.
Shake the module harness and sensor harness while checking the resistance between the sensor connector signal Pin 3 Circuit 772 (LB) and chassis ground.

Is resistance greater than 1 ohm?

Yes	No
REPLACE speed sensor. If the fault still occurs REPLACE controller.	REPAIR short-to-ground in the speed sensor signal circuit. REFER to the Electrical Schematics in this section.

PINPOINT TEST F: TRANSFER CASE CLUTCH DIAGNOSIS

F1 BAD OR INTERMITTENT POWER TO MAGNETIC CLUTCH

Check the voltage at the transfer case motor connector:

Disconnect the transfer case motor harness connector from the transfer case housing.
Set the voltmeter to the 20 VDC scale.
Key to RUN.
Shake the transfer case motor harness and check for battery voltage between the transfer case harness Pin 10 and chassis ground.

Is voltage present and is it steady or intermittent?

Yes	No
REPAIR short to B+ on the clutch circuit or REPLACE control module. REFER to the Electrical Schematics in this section.	GO to F2.

F2 MAGNETIC CLUTCH CIRCUIT SHORT-TO-GROUND

Check for a short-to-ground on the clutch circuit:

Key off.
Disconnect the module harness connector from the electronic shift module C1.
Set the ohmmeter to the 20 ohm scale.
Shake the module harness connector and check the resistance between electronic shift control module Pin 6 and chassis ground.

Is resistance intermittent and below 1 ohm?

Yes	No
REPAIR short-to-ground on the clutch circuit. REFER to the Electrical Schematics in this section.	GO to F3.

F3 CONTINUITY TESTING OF MAGNETIC CLUTCH CIRCUIT

Check for an open on the clutch circuit:

Key off.
Disconnect the transfer case harness connector from the transfer case motor.
Set the ohmmeter to the 20 ohm scale.
Shake the transfer case motor harness connector and check the resistance of Pin 1 at the transfer case motor harness Circuit 779 (BRN) and transfer case ground.

Is resistance between 1.5 and 4 ohms?

Yes	No
Continuity OK.	REPAIR open in clutch circuit or REPLACE clutch.