P0255

P0255-INJECTION PUMP FUEL CONTROL CIRCUIT PERFORMANCE





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

Theory of Operation

The Fuel Control Actuator (FCA) is an electronically controlled solenoid valve. The Powertrain Control Module (PCM) provides a PWM driver circuit and ground circuit to the FCA. The PCM 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 PCM to force the Fuel Control Actuator into a region where this fault code becomes active. The PCM 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 PCM turns off the MIL lamp after the diagnostic runs and passes in 4 consecutive drive cycles.

- When Monitored:
Continuously with the engine running.

- Set Condition:
The Powertrain Control Module (PCM) detects a discrepancy between the PWM signal supplied to the Fuel Control Actuator and the PWM returned from the 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 75 seconds.
4. Start the engine and let idle for up to two minutes.
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. CHECK FOR HIGH RESISTANCE IN THE (K366) FUEL CONTROL ACTUATOR DRIVER CIRCUIT




1. Turn the ignition off.
2. Disconnect the Fuel Control Actuator harness connector.
3. Disconnect the PCM C1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

4. Measure the resistance of the (K366) FCA Driver circuit between the Fuel Control Actuator harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 3

No

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

3. CHECK FOR HIGH RESISTANCE IN THE (K365) FUEL CONTROL ACTUATOR RETURN CIRCUIT




1. Measure the resistance of the (K365) FCA Return circuit between the Fuel Control Actuator harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 4

No

- Repair the (K365) FCA Return circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. FUEL CONTROL ACTUATOR
1. Reconnect the PCM C1 harness connector.
2. Replace the Fuel Control Actuator.
3. Turn the ignition on and clear any DTCs.
4. Start the engine and let idle for at least two minutes.
5. With the scan tool, read DTCs.

Did the DTC reset?

Yes

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

No

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