Test M: Fuel Pump Monitor/Control: Testing

CAUTION: The Powertrain Control Module (PCM) harness connectors must be properly seated and the connector latch properly attached to eliminate possible driveability concerns or a no-start condition. Installing PCM connectors on an angle may cause a bad connection, misdiagnosis and damaged components. Install the connector on where the lever pivots and seats itself. Apply light pressure to get the connector into position on the PCM lever to fully seat the connector.

NOTE: When the PCM engine harness connector is disconnected additional DTCs will be set. All DTCs must be cleared before returning the vehicle to service.

1) Preliminary Diagnosis For DTCs P0230, P0231 & P0232

Perform the visual inspection. Connect the scan tool. Retrieve and record all DTCs. Record freeze frame data. Clear all DTCs. Perform the KOEO ON-DEMAND SELF-TEST under QUICK TEST. Are any DTCs retrieved? If yes, for P0230, go to next step. For P0231, go to step 6). For P0232, go to step 10). If no, unable to duplicate condition. Check for loose connections, damaged or corroded terminals or pins. Wiggle harness attempting to recreate the fault. Repair as necessary. See TROUBLE SHOOTING - NO CODES - 6.0L DIESEL article if a driveability concern exists.

2) DTC P0230

Possible causes are:
- Faulty fuel pump relay.
- Circuit open.
- Faulty PCM.
Key off. Disconnect central junction box electrical connector C270F. Key on. Measure the voltage between central junction box connector C270F terminal No. 10, component side and ground. See Figure. Is the voltage greater than 10.5 volts? If yes, go to next step. If no, replace the central junction box. Restore the vehicle. Clear DTCs and retest the system.

3) Check Fuel Pump Relay Control Circuit For A Short To Voltage

Key on. Disconnect the PCM body harness electrical connector C1381A. Measure the voltage between central junction box connector C270F terminal No. 10, harness side and ground. Is the voltage less than 0.2 volt? If yes, go to next step. If no, repair short to voltage. Restore the vehicle. Clear DTCs and retest the system.

4) Check Fuel Pump Relay Control Circuit For A Short To Ground

Measure the resistance between central junction box connector C270F terminal No. 10, harness side and ground. Is the resistance greater than 10,000 ohms? If yes, go to next step. If no, repair short to ground in control circuit. Restore the vehicle. Clear DTCs and retest the system.

5) Check Fuel Pump Control Circuit For An Open

Measure the resistance between central junction box connector C270F terminal No. 10, harness side and PCM body harness connector C1381A terminal No. 5. See CONTROL MODULE CONNECTOR IDENTIFICATION . Is the resistance less than 0.5 ohm? If yes, replace the PCM. Restore the vehicle. Clear DTCs and retest the system. If no, repair open in control circuit. Restore the vehicle. Clear DTCs and retest the system.

6) DTC P0231

Possible causes are:
- Blown fuse.
- Open inertia switch.
- Open fuel pump monitor circuit.
- Faulty fuel pump relay.
Check fuse. Check inertia switch (button must be pushed inward). Is the fuse blown? If yes, replace the fuse. If the fuse blows when the key is turned on, install a new central junction box. Restore the vehicle. Clear DTCs and retest the system. If no, go to next step.

7) Check Inertia Switch

Key off. Disconnect inertia switch electrical connector. Install a test lamp between inertia switch electrical connector terminal No. 1 and ground. See Figure or Figure . Key on. Does the test lamp light for 20 seconds then go out? If yes, go to step 9). If no, go to next step.

8) Check Fuel Pump Monitor Circuit For An Open

Disconnect the central junction box electrical connector C270A. Measure the resistance between central junction box connector C270A terminal No. 22 and inertia connector terminal No. 1. Is the resistance less than 0.5 ohm? If yes, replace the central junction box. Restore the vehicle. Clear DTCs and retest the system. If no, repair open in circuit. Restore the vehicle. Clear DTCs and retest the system.

9) Check Fuel Pump Monitor Circuit For An Open

Disconnect the PCM. Measure the resistance between the inertia switch connector terminal No. 2 and PCM connector C1381A terminal No. 19. See CONTROL MODULE CONNECTOR IDENTIFICATION . Is the resistance less than 0.5 ohm? If yes, replace the PCM. Restore the vehicle. Clear DTCs and retest the system. If no, repair open in monitor circuit. Restore the vehicle. Clear DTCs and retest the system.

10) DTC P0232

Possible causes are:
- Shorted fuel pump relay.
- Fuel pump monitor circuit short to voltage.
If DTC P0230 is also present, go to step 2). Does the fuel pump run all the time? If yes, go to next step. If no, go to step 12).

11) Check Fuel Pump Relay

Disconnect the central junction box electrical connector C270A. Does the fuel pump stop running? If yes, replace the central junction box. Restore the vehicle. Clear the DTCs and retest the system. If no, go to next step.

12) Check Circuit Between The Inertia Switch & Fuel Pump Relay For A Short To Voltage

Disconnect the inertia switch electrical connector. Measure the voltage between the inertia switch connector terminal No. 1 and ground. See Figure or Figure . Is the voltage less than 0.2 volt? If yes, go to next step. If no, repair short to voltage in circuit. Restore the vehicle. Clear the DTCs and retest the system.

13) Check Circuit Between The Inertia Switch & PCM For A Short To Voltage

Key off. Disconnect the PCM body harness connector C1381A. Disconnect the fuel pump electrical connector. Key on. Measure the voltage between the inertia switch connector terminal No. 2 and ground. Is the voltage less than 0.2 volt? If yes, replace the PCM. Restore the vehicle. Clear the DTCs and retest the system. If no, repair short to voltage in circuit. Restore the vehicle. Clear the DTCs and retest the system.