Camshaft Position (CMP) Sensor

1996 PCED OBDI

SECTION 18: Diesel Diagnosis — 7.3L DI Engine

G: Camshaft Position (CMP) Sensor

G1 CLEAR AND ATTEMPT TO REGENERATE DTC 0344, 0341 OR 0340

Plug in NGS Tester.
Clear continuous DTCs with NGS Tester.
Crank engine while monitoring rpm PID.

Does PID indicate crank rpm?

Yes	No
GO to G2.	GO to G3.

G2 RERUN CONTINUOUS FOR DTC 0344 OR 0341

Warm up engine to normal operating temperature.
Increase rpm to 3300 rpm for 2 minutes.
Key off.
Rerun continuous codes.

Are DTC 0344 or 0341 present?

Yes	No
GO to G3.	Fault is intermittent. GO to G12.

G3 CHECK CMP SIGNAL RETURN CIRCUIT 796 (LB)

Unplug CMP sensor.
Key off.
Check resistance between Pin A on the CMP connector and chassis ground.

Is resistance less than 5 ohms?

Yes	No
Ground is OK. GO to G4.	GO to G9.

G4 CHECK CMP CIRCUIT 351 (BR/W) FOR VREF

(CMP sensor unplugged)
Key on.
Check voltage between harness connector Pin B and chassis ground.

Is 5 volts ± .5 volts present?

Yes	No
Circuit 351 (BR/W) is OK. GO to G5.	SERVICE VREF circuitry. GO to B1.

G5 CHECK CMP CIRCUIT 795 (DG) FOR B+

(CMP sensor unplugged)
Key on.
Check voltage between harness connector Pin C and chassis ground.

Is B+ present?

Yes	No
GO to G6.	Circuit 795 (DG) is shorted or open. GO to G7.

G6 CHECK CMP CIRCUIT 795 (DG) FOR SHORT TO B+

(CMP sensor unplugged)
Key off.
Unplug PCM.
Inspect 104 pin connector and repair if required.
Key on.
Check voltage between harness connector Pin C and chassis ground.

Is B+ present?

Yes	No
SERVICE short to B+ in Circuit 795 (DG). REASSEMBLE system. CONFIRM fix with NGS Tester PID "RPM" and by repeating G1 and G2.	Circuit 795 (DG) is OK. REPLACE CMP sensor.

G7 CHECK CIRCUIT 795 (DG) FOR SHORT TO GROUND

(CMP sensor unplugged)
Key off.
Unplug PCM.
Inspect 104 pin connector and repair if required.
Key on.
Check resistance between connector point C and chassis ground.

Is resistance less than 5 ohms?

Yes	No
SERVICE short to ground in Circuit 795 (DG). REASSEMBLE system. CONFIRM fix with NGS Tester PID "RPM" and by repeating G1 and G2.	GO to G8.

G8 CHECK CIRCUIT 795 (DG) FOR OPEN

(CMP sensor unplugged)
(PCM unplugged)
Key off.
Attach 104 pin breakout box.
Leave PCM disconnected.
Key on.
Check resistance between harness connector Pin C and breakout box Pin 49.

Is resistance less than 5 ohms?

Yes	No
Open is at PCM Pin 49. INSPECT PCM connector and PCM pins. SERVICE as necessary. REASSEMBLE system. GO to G11.	REPAIR open in Circuit 795 (DG). REASSEMBLE system. CONFIRM fix with NGS Tester PID "RPM" and by repeating G1 and G2.

G9 CHECK FOR OPEN IN CMP GROUND CIRCUIT 796 (LB)

(CMP sensor unplugged)
Key off.
Unplug PCM.
Inspect 104 pin connector and PCM pins and repair as required.
Install breakout box.
Leave PCM disconnected.
Measure resistance from PCM Test Pin 65 to harness connector Pin A.

Is resistance less than 5 ohms?

Yes	No
Circuit 796 (LB) is OK. GO to G10.	SERVICE open in Circuit 796 (LB). REASSEMBLE system. CONFIRM fix with NGS Tester PID "RPM" and by repeating G1 and G2.

G10 CHECK FOR CMP GROUND THROUGH PCM

(CMP unplugged)
(Breakout box attached)
Key off.
Attach PCM to breakout box.
Measure resistance from PCM Test Pins 25, 51, 76, 77 and 103 to ground.

Is resistance less than 5 ohms?

Yes	No
PCM internal ground not supplied to Pin 65. REASSEMBLE system. GO to G11.	REPAIR open in Circuit 570 (BK/W) and Circuit 57 (BK) as required. REASSEMBLE system. CONFIRM fix with NGS Tester PID "RPM" and by repeating G1 and G2.

G11 CONFIRM PCM FAULT

Rerun G1 and G2.

Are faults still present?

Yes	No
REPLACE PCM and RERUN.	System is OK.

G12 FIND INTERMITTENT

Key off.
Unplug PCM.
Inspect 104 pin connector and PCM pins and repair as required.
Install breakout box.
Attach PCM to breakout box.
Unplug the IDM relay in the engine compartment power distribution box to prevent engine from starting.
Run voltmeter test leads between breakout box Test Pins 49 and 65.
Rotate engine by hand until voltage toggles from B+ to between 0.3 and 2.7 volts.

Did lower voltage toggle fall between 0.3 and 2.8 volts?

Yes	No
GO to G13.	GO to G3.

G13 CHECK HARNESSES FOR INTERMITTENT

(Breakout box installed)
(PCM attached to breakout box)
(IDM relay unplugged)
(Voltmeter test leads between breakout box Test Pins 49 and 65)
Rotate engine by hand until voltage stays at lower toggle of between 0.3 and 2.7 volts.
Wiggle harnesses and watch for voltage jump to B+ or 0.0 volts.

Did voltage jump to B+ or 0.0 volts?

Yes	No
DETERMINE source of intermittent and REPAIR. CONFIRM fix with NGS PID "RPM" and by rerunning G1 and G2.	Intermittent not found. REASSEMBLE system using dielectric grease. CHECK with NGS Tester PID "RPM" and by rerunning G1 and G2.