P0251

P0251-INJECTION PUMP FUEL VALVE FEEDBACK





For a complete wiring diagram Refer to Diagrams/Electrical.

Theory of Operation


The Fuel Control Actuator (FCA) is an electronically controlled solenoid valve. The circuit is a PWM driver in the ECM that controls the FCA. The actuator is grounded in the ECM. 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. The ECM illuminates the MIL 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 ECM detects a discrepancy between the PWM supplied to the Electronic Fuel Control Actuator and the PWM returned from the Electronic Fuel Control Actuator. Although this is primary 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.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview


1. FUEL PRESSURE
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


- Document DTC and freeze frame data and attempt to duplicate complaint.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test


If the psi is higher than setpoint


- Go To 4


If the psi is lower than setpoint


- Go To 2



2. LIFT PUMP
Perform the lift pump flow test.In-Tank Fuel Lift Pump Flow/Diagnostic Test Procedure
Did the test pass?

Yes


- Go To 3


No


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



3. INJECTOR RETURN FLOW
Perform the Injector return flow test.Injector Return Flow Test
Did the test pass?

Yes


- Go To 4


No


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


Diagnostic Test


4. FUEL PUMP




Ignition on, engine not running.
Disconnect the Fuel Control Actuator (FCA) harness connector.
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.
Observe the test light.
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 Fuel Pump.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test


No


- Go To 5



5. (K365) FUEL CONTROL ACTUATOR DRIVER OPEN




Turn the ignition off.
Disconnect the ECM harness connectors.

NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance of the FCA driver circuit between the electronic fuel control actuator harness connector and the ECM harness connector.
Is the resistance less than 10 Ohms?

Yes


- Go To 6


No


- Repair the (K365) Fuel Control Actuator Driver circuit OPEN.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test



6. (K366) RETURN CIRCUIT OPEN




Measure the resistance of the (K366) return circuit between the FCA harness connector and the ECM harness connector.
Is the resistance less than 10 Ohms?

Yes


- Go To 7


No


- Repair or replace the engine wiring harness.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test



7. (K365) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGE




Measure the voltage between the (K365) FCA driver circuit in the FCA harness connector and battery negative.
Is the voltage greater than 1 volts?

Yes


- Repair the (K365) FCA driver circuit shorted to external voltage.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test


No


- Go To 8



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




Measure the voltage between the (K366) FCA return circuit in the FCA harness connector and battery negative.
Is the voltage greater than 1 volts?

Yes


- Repair the (K366) FCA return circuit shorted to external voltage.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test


No


- Go To 9



9. (K366) FCA RETURN CIRCUIT SHORTED TO (K365) FCA DRIVER CIRCUIT




Measure the Resistance between the return circuit in the FCA harness connector and Driver circuit.
Is the resistance less than 10 Ohms?

Yes


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


No


- Go To 10



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




Measure the resistance between the (K365) FCA driver circuit in the FCA harness connector and battery negative.
Is the resistance less than 10 Ohms?

Yes


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


No


- Go To 11



11. (K365) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO ANOTHER CIRCUIT




Measure the resistance between the (K365) FCA driver circuit in the ECM harness connector and all other circuits in the ECM connectors.
Is the resistance less than 10 Ohms?

No


- Go To 12


Yes


- Repair the (K365) FCA driver circuit shorted to another circuit.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test



12. (K366) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO ANOTHER CIRCUIT




Measure the resistance between the (K366) FCA Return circuit in the ECM harness connector and all other circuits in the ECM connectors.`
Is the resistance less than 10 Ohms?

No


- Go To 13


Yes


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



13. ECM




Reconnect the ECM harness connectors.
Ignition on, engine not running.
Disconnect the Electronic Fuel Control Actuator connector.
Connect an incandescent test light across the Fuel Control Actuator driver pin and the Fuel Control Actuator return wire at the fuel control actuator connector.
Observe the test light.
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: Compare test light brightness to that of a direct connection to the battery.

Did the light flash brightly?

Yes


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


No


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