P0628

P0628-FUEL PUMP CONTROL CIRCUIT LOW





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 TIPM to turn on the Fuel Lift Pump. The TPIM 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 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 off by the ECM, 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 30 seconds.
5. Turn the ignition on.
6. With the scan tool, read DTCs.

Did the DTC reset?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION - DIESEL (Diagnostic Procedure). Intermittent Condition Test

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




1. Turn the ignition off.
2. Disconnect the ECM C2 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 ECM C2 harness connector.

Is there any voltage present?

Yes

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

No

- Go To 3

3. (K31) FUEL LIFT PUMP CONTROL CIRCUIT OPEN




1. Turn Ignition off.
2. Disconnect the TIPM C1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

3. Measure the resistance of the (K31) Fuel Lift Pump Control circuit between the ECM C2 harness connector and the TIPM C1 harness connector.

Is the resistance less than 10.0 ohms?

Yes

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

No

- Go To 4

4. ECM/TIPM




1. Reconnect the ECM C2 harness connector.
2. Turn the ignition on, engine off.
3. Using a 12-volt test light connected to ground, probe the (K31) Fuel Lift Pump Control circuit at the TIPM C1 harness connector.
4. Toggle the lift pump actuator with the scan tool.

NOTE: The test light must illuminate brightly.

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

No

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