P0629

P0629-FUEL PUMP CONTROL CIRCUIT HIGH





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

Theory of Operation

The Fuel Lift Pump Control circuit is a high side driver inside the Engine Control Module (ECM). The ECM sends a 12-volt signal to the Totally Integrated Power Module (TIPM) to turn on the Fuel Lift Pump. The TIPM sends a 12-volt feed to the Fuel Lift Pump. The Fuel Lift Pump grounds through a dedicated ground circuit. With the engine running, the pump has a 100% duty cycle. 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 ECM will turn off the MIL lamp once the diagnostic runs and passes in 4 consecutive drive cycles.

- When Monitored:
While the key is on.

- Set Condition:
The Fuel Lift Pump is commanded on by the Engine Control Module (ECM), but feedback voltage is low.





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 30 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 diagnostic procedure. Intermittent Condition Test.

2. (K31) FUEL LIFT PUMP CONTROL CIRCUIT SHORTED TO GROUND




1. Turn the ignition off.
2. Disconnect the ECM C2 harness connector.
3. Disconnect the TIPM C1 harness connector.
4. Using an Ohmmeter, measure the resistance between ground and the (K31) Fuel Lift Pump Control circuit at the ECM C2 harness connector.

Is the resistance below 10.0 Ohms?

Yes

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

No

- Go To 3

3. ECM
1. Reconnect the ECM C2 and TIPM C1 harness connectors.
2. Using a back probing tool 6801, back probe the (K31) Fuel Lift Pump Control circuit at the TIPM C1 harness connector.
3. Turn the ignition on.
4. With the scan tool toggle the Fuel Lift Pump actuator.
5. Using a 12-volt test light connected to ground, probe the (K31) Fuel Lift Pump Control circuit at the TIPM harness connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Does the test light cycle on and off brightly?

Yes

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

No

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