Test Procedure

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Z1 PRELIMINARY DIAGNOSIS FOR DTC P0603

Possible causes:
- battery or PCM previously disconnected
- battery cables loose or poor connections
- battery discharged
- open or short to ground in the KAPWR circuit
- PCM reprogramming or reflash
- PCM
Key on, engine off.
Clear the DTCs.
Cycle the ignition switch off and on.
Perform the self-test.

IS DTC P0603 PRESENT?

Yes	No
Go to Z2.	Unable to duplicate condition. CHECK for loose connections, damaged or corroded pins. REFER to SYMPTOM CHARTS - 6.0L DIESEL for driveability concerns.

Z2 CHECK THE CHARGING SYSTEM

Check the battery and charging system. Refer to the appropriate GENERATORS AND REGULATORS article.

IS A CONCERN PRESENT?

Yes	No
REPAIR as necessary. Refer to the appropriate GENERATORS AND REGULATORS article.	Go to Z3.

Z3 CHECK THE KAPWR CIRCUIT FOR VOLTAGE

Key off.
Disconnect the PCM body harness connector.
Measure the voltage between the PCM body harness connector pin 40, harness side and ground.

IS THE VOLTAGE GREATER THAN 10.5 VOLTS?

Yes	No
CHECK for loose connections, damaged or corroded pins. WIGGLE harness attempting to recreate fault. CLEAR the DTCs and REPEAT the self-test. If DTC P0603 is present again, INSTALL a new PCM.	REPAIR the circuit.