P0251

P0251-CP3 PUMP REGULATOR CONTROL

For complete wiring diagrams refer to Diagrams/Electrical.

- When Monitored:

When the ignition is on.

- Set Condition:

The ECM detects a discrepancy between the PWM signal supplied to the Fuel Control Actuator (FCA) and the PWM signal returned from the Fuel Control Actuator.

Possible Causes:

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

1. (K604) FUEL CONTROL ACTUATOR DRIVER OPEN/HIGH RESISTANCE






Turn the ignition off.

Disconnect the ECM C1 harness connectors.

NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance of the (K604) FCA Driver circuit between the Fuel Control Actuator harness connector and the ECM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 2

No

- Repair the (K604) Fuel Control Actuator (FCA) Driver circuit for an open or high resistance.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

2. (K65) FUEL CONTROL ACTUATOR RETURN CIRCUIT OPEN/HIGH RESISTANCE






Measure the resistance of the (K65) FCA Return circuit between the FCA harness connector and the ECM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 3

No

- Repair the (K65) FCA Return circuit for an open or high resistance.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

3. (K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGE





Turn the ignition on.

Measure the voltage between the (K604) FCA Driver circuit in the FCA harness connector and battery negative.

Is the voltage above 1 Volt?

Yes

- Repair the (K604) FCA Driver circuit shorted to external voltage.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 4

4. (K65) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO EXTERNAL VOLTAGE






Measure the voltage between the (K65) FCA Return circuit in the FCA harness connector and battery negative.

Is the voltage above 1 Volt?

Yes

- Repair the (K65) FCA Return circuit shorted to external voltage.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 5

5. (K65) FCA RETURN CIRCUIT SHORTED TO (K604) FCA DRIVER CIRCUIT






Turn the ignition off.

Measure the resistance between the (K65) Return circuit and the (K604) FCA Driver circuit in the FCA harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 6

No

- Repair the (K65) FCA Return circuit shorted to (K604) FCA Driver circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

6. (K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO GROUND





Measure the resistance between ground and the (K604) FCA driver circuit in the FCA harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 7

No

- Repair the (K604) FCA driver circuit shorted to ground.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

7. (K604) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO ANOTHER CIRCUIT






Disconnect the ECM C2 harness connector.

Measure the resistance between the (K604) FCA driver circuit in the ECM harness connector and all other circuits in the ECM connectors.

Is the resistance above 10k Ohms?

No

- Go To 8

Yes

- Repair the (K604) FCA Driver circuit for a short to the circuit that measured below 10k Ohms.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

8. (K65) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO ANOTHER CIRCUIT






Measure the resistance between the (K65) FCA Return circuit in the ECM harness connector and all other circuits in the ECM connectors.`

Is the resistance above 10k Ohms?

No

- Go To 9

Yes

- Repair the (K65) FCA Return circuit for a short to the circuit that measured below 10k Ohms.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

9. ENGINE CONTROL MODULE






Reconnect the ECM harness connectors.

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.

Turn the ignition on, engine not running.

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 ignition on.

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

Did the light flash brightly?

Yes

- Replace the Fuel Control Actuator.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Replace the Engine Control Module.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test