P0629

P0629-FUEL PUMP CONTROL CIRCUIT HIGH

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 on by the Powertrain Control Module (PCM), 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 75 seconds.
5. Turn the ignition on.
6. With the scan tool, read DTCs.

Did the DTC return?

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 GROUND
1. Turn the ignition off.
2. Disconnect the PCM C2 harness connector.
3. Disconnect the TIPM C6 harness connector.
4. Measure the resistance between ground and the (K31) Fuel Lift Pump Control circuit at the PCM C2 harness connector.

Is the resistance below 10k Ohms?

Yes

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

No

- Go To 3

3. CHECK THE (K31) FUEL LIFT PUMP CONTROL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance of the (K31) Fuel Lift Pump Control circuit between the PCM C2 harness connector and the TIPM C6 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Repair the (K31) Fuel Lift Pump Control circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 4

4. POWERTRAIN CONTROL MODULE
1. Reconnect the PCM C2 and TIPM C6 harness connectors.
2. Using a back probing tool, back probe the (K31) Fuel Lift Pump Control circuit at the TIPM C6 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 C6 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 Totally Integrated Power Module (TIPM).
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

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