P0628

P0628-FUEL PUMP CONTROL CIRCUIT LOW

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Fuel Lift Pump Control circuit is a low side driver inside the Powertrain Control Module (PCM). The PCM sends a ground signal to the Totally Integrated Power Module (TIPM). The TIPM then sends a 12 Volt feed to the Fuel Lift Pump. The Fuel Lift Pump grounds through a dedicated ground circuit. The MIL lamp and ETC lamp will illuminate immediately after this diagnostic runs and fails. During this time, the customer may experience engine stumble/stall or low power due to lack of fuel supply to the high pressure system. The PCM will turn off the MIL lamp once the diagnostic runs and passes in four consecutive drive cycles.

- When Monitored:
While the key is on.

- Set Condition:
The Fuel Lift Pump is commanded off by the PCM, but feedback voltage is high.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC
1. Turn the ignition on.
2. With the scan tool, record all Freeze frame data.
3. With the scan tool, erase DTCs.
4. Turn the ignition off for 75 seconds.
5. Turn the ignition on.
6. With the scan tool, read DTCs.

Did the DTC reset?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION - 6.7L diagnostic procedure. Intermittent Condition Test

2. CHECK THE (K31) FUEL LIFT PUMP CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the PCM C2 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

3. Turn the ignition on.
4. Measure for voltage on the (K31) Fuel Lift Pump Control circuit at the PCM C2 harness connector.

Is there any voltage present?

Yes

- Repair the (K31) Fuel Lift Pump Control circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 3

3. CHECK THE PCM/TIPM
1. Turn Ignition off.
2. Disconnect the TIPM C6 harness connector.
3. Reconnect the PCM C2 harness connector.
4. Turn the ignition on, engine off.
5. Using a 12-volt test light connected to 12 Volts, probe the (K31) Fuel Lift Pump Control circuit at the TIPM C1 harness connector.
6. Toggle the lift pump actuator with the scan tool.

NOTE: The test light must illuminate brightly.

7. Compare the brightness to that of a direct connection to the battery.

Does the test light cycle on and off and illuminate brightly?

Yes

- Replace the Totally Integrated Power Module.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

No

- Replace the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.