Test Procedure

DF1 DIAGNOSTIC TROUBLE CODE (DTC) P0500 AND P1501

Possible causes:
- VSS signal circuit open
- VSS signal circuit shorted to ground
- PCM
ABS module
Key ON, engine OFF.
Access the ABS module.
Carry out the self-test diagnostics for the ABS module.

Are any ABS module DTCs present?

Yes	No
REFER to ANTI-LOCK CONTROL to continue diagnosis.	GO to DF2.

DF2 CHECK THE PCM VEHICLE SPEED SIGNAL INPUT

Does the VSS PID increase as the vehicle speed is increased and decrease as the vehicle speed is decreased?

Yes	No
UNABLE to duplicate the condition. CHECK for a loose connection, and damaged or corroded terminals. WIGGLE the harness attempting to recreate the fault. REPAIR as necessary. REFER to SYMPTOM CHARTS - 6.0L DIESEL if a driveability concern exists.	GO to DF3.

DF3 CHECK THE VEHICLE SPEED SIGNAL CIRCUIT FOR AN OPEN

Key OFF.
Disconnect the PCM.
Disconnect the ABS module.
Measure the resistance between the PCM body connector pin 35, harness side and the ABS module pin 21 (F-Super Duty) or pin 11 (Excursion), harness side.

Is the resistance less than 5 ohms?

Yes	No
GO to DF4.	REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.

DF4 CHECK THE VEHICLE SPEED SIGNAL CIRCUIT FOR A SHORT TO GROUND

Measure the resistance between the PCM body connector pin 35, harness side and ground.

Is resistance greater than 10, 000 ohms?

Yes	No
GO to DF5.	REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.

DF5 CHECK THE VEHICLE SPEED SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE

Key ON, engine OFF.
Measure the voltage between the PCM body connector pin 35, harness side and ground.

Is any voltage indicated?

Yes	No
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.	CLEAR the DTCs. REPEAT the self-test. If the DTC is present again, INSTALL a new PCM.