P0628

P0628-FUEL PUMP CONTROL CIRCUIT LOW







Theory of Operation

The Fuel Lift Pump Control circuit is a low side driver inside the Powertrain Control Module (PCM). Do to the nature in which this monitor runs, a short to voltage in the (K31) Fuel Lift Pump Control circuit will set this DTC. The Totally Integrated Power Module (TIPM) sends a 12 Volt signal to the PCM on the (K31) Fuel Lift Pump Control circuit at ignition on. The PCM grounds the control circuit from the TPIM to command the Fuel Lift Pump on. The TPIM then sends a 12 Volts 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 Powertrain Control Module (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 TIPM 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 TOTALLY INTEGRATED POWER MODULE OUTPUT
1. Reconnect the TIPM C2 harness connector.
2. Turn the ignition off.

NOTE: Be careful to use only an appropriate back probing tool so as not to damage the terminal or connector in the next step.

3. Using a Voltmeter connected to ground, back probe the (K31) Fuel Lift Pump Control circuit at the TIPM C2 harness connector.
4. Turn the ignition on.

Does the Voltmeter read above 9.5 Volts with the ignition on?

Yes

- Go To 4

No

- Replace the Totally Integrated Power Module (TIPM).
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. POWERTRAIN CONTROL MODULE
1. With the scan tool, toggle the Fuel Lift Pump actuator on and off.

Does the Voltmeter read above 9.5 Volts with the lift pump toggled off and 0 Volts with the lift pump toggled on?

Yes

- Disconnecting and reconnecting the TIPM harness connector may have fixed the problem. Perform the INTERMITTENT CONDITION - 6.7L diagnostic procedure. Intermittent Condition Test.

No

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