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P0251






P0251-INJECTION PUMP FUEL VALVE FEEDBACK





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

Theory of Operation

The Fuel Control Actuator (FCA) is an electronically controlled solenoid valve. The Engine Control Module (ECM) provides a PWM driver circuit and ground circuit to the FCA. The ECM varies the current to this valve to provide the correct fuel flow to the High Pressure Pump based on operating conditions. The FCA is a normally open valve. High circuit resistance may cause fuel pressure to be higher than commanded at light loads. Although this is primarily an electrical diagnostic check, fuel supply issues and high pressure leaks can cause the ECM to force the Fuel Control Actuator into a region where this fault code becomes active. The ECM illuminates the MIL lamp and the ETC lamp immediately after the diagnostic runs and fails. During this time the customer may experience low power. The ECM turns off the MIL lamp after the diagnostic runs and passes in 4 consecutive drive cycles.

- When Monitored:
When the ignition is on.

- Set Condition:
The Engine Control Module (ECM) detects a discrepancy between the PWM signal supplied to the Electronic Fuel Control Actuator and the PWM returned from the Electronic Fuel Control Actuator.





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

1. ACTIVE DTC
1. Ignition on, engine not running.
2. Record freeze frame data and clear DTCs.
3. Turn the ignition off for 30 seconds.
4. Turn the ignition on.
5. 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. (K365) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO VOLTAGE




1. Turn the ignition off.
2. Disconnect the Fuel Control Actuator harness connector.
3. Turn the ignition on.
4. Measure the voltage of the (K365) FCA Driver circuit at the FCA harness connector.

NOTE: The (K365) FCA Driver circuit will read approximately six volts at initial key on and then drop to approximately three volts.

Is the voltage reading near battery voltage?

Yes

- Repair the short to voltage in the (K365) FCA Driver circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 3

3. (K366) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO VOLTAGE




1. Measure the voltage of the (K366) FCA Return circuit at the FCA harness connector.

NOTE: The (K366) FCA Return circuit should not have voltage present.

Is there any voltage present?

Yes

- Repair the short to voltage in the (K366) FCA Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 4

4. (K365) FUEL CONTROL ACTUATOR DRIVER CIRCUIT OPEN




1. Turn the ignition off.
2. Disconnect the ECM C1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

3. Measure the resistance of the (K365) FCA Driver circuit between the Fuel Control Actuator harness connector and the ECM C1 harness connector.

Is the resistance below 10.0 Ohms?

Yes

- Go To 5

No

- Repair the open or high resistance in the (K365) Fuel Control Actuator Driver circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

5. (K366) FUEL CONTROL ACTUATOR RETURN CIRCUIT OPEN




1. Measure the resistance of the (K366) FCA Return circuit between the Fuel Control Actuator harness connector and the ECM C1 harness connector.

Is the resistance below 10.0 Ohms?

Yes

- Go To 6

No

- Repair the open or high resistance in the (K366) Fuel Control Actuator Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

6. (K365) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO GROUND




1. Measure the resistance between ground and the (K365) FCA Driver circuit at the FCA harness connector.

Is the resistance below 10k Ohms?

Yes

- Repair the short to ground in the (K365) FCA Driver circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 7

7. (K365) FCA DRIVER CIRCUIT SHORTED TO THE (K366) FCA RETURN CIRCUIT




1. Measure the Resistance between the (K365) FCA Driver circuit and the (K366) FCA Return circuit at the Fuel Control Actuator harness connector.

Is the resistance below 10k Ohms?

Yes

- Repair the short between the (K365) FCA Driver circuit and the (K366) FCA Return circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 8

8. FUEL PRESSURE
1. Reconnect the Fuel Control Actuator harness connector.
2. Reconnect the ECM C1 harness connector.
3. Turn the ignition on and clear any DTCs.
4. Start the engine.
5. With the scan tool watch fuel pressure vs setpoint with the engine at idle.

Is the pressure within 500 psi ± of set point?

If psi is within 500 psi

- Using the freeze frame data, attempt to duplicate complaint.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

If the psi is higher than setpoint,

- Go To 11

If the psi is lower than setpoint,

- Go To 9

9. LIFT PUMP
1. Perform the LIFT PUMP FLOW TEST.Component Tests and General Diagnostics

Did the LIFT PUMP FLOW TEST pass?

Yes

- Go To 10

No

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

10. INJECTOR RETURN FLOW
1. Perform the INJECTOR RETURN FLOW TEST. Injector Return Flow Test

Did the INJECTOR RETURN FLOW TEST pass?

Yes

- Go To 11

No

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

11. HIGH PRESSURE FUEL PUMP




1. Turn the ignition on, engine not running.
2. Disconnect the Fuel Control Actuator harness connector.
3. Connect an incandescent test light across the Fuel Control Actuator Driver circuit and the Fuel Control Actuator return circuit at the Fuel Control Actuator harness connector.
4. Observe the test light.
5. The ECM will perform a self test of the circuit which should momentarily flash the test light brightly, one time, approximately 20 seconds after being connected.

NOTE: Check connectors - Clean/repair as necessary.

NOTE: Compare test light brightness to that of a direct connection to the battery.

Did the light flash brightly?

Yes

- Replace the High Pressure Fuel Pump.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Replace and program the Engine Control Module (ECM).
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

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