P0251
P0251-CP3 PUMP REGULATOR CONTROLP0251 - CP3 Pump Regulator Control:
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.
POSSIBLE CAUSES
- Fuel pump
- (K181) Fuel control actuator driver open
- (K31) Return circuit open from FCA to ECM
- (K181) Fuel control actuator driver circuit shorted to external voltage
- (K31) Fuel control actuator return circuit shorted to external voltage
- (K31) FCA return circuit shorted to (K181) FCA driver circuit
- (K181) Fuel control actuator driver circuit shorted to ground
- (K181) Fuel control actuator driver circuit shorted to another circuit
- (K31) Fuel control actuator return circuit shorted to another circuit
- Intermittent condition
- ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. 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.
- Compare test light brightness to that of a direct connection to the battery.
Q: Did the light flash brightly?
YES: Replace the Fuel Pump. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Go To 2
2. (K181) 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.
Q: Is the resistance less than 10 Ohms?
YES: Go To 3
NO: Repair the (K181) Fuel Control Actuator Driver circuit OPEN. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
3. (K31) RETURN CIRCUIT OPEN
Measure the resistance of the (K31) return circuit between the FCA harness connector and the ECM harness connector.
Q: Is the resistance less than 10 Ohms?
YES: Go To 4
NO: Repair or replace the engine wiring harness. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
4. (K181) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGE
Measure the voltage between the (K181) FCA driver circuit in the FCA harness connector and battery negative.
Q: Is the voltage greater than 1 volts?
YES: Repair the (K181) FCA driver circuit shorted to external voltage.
NO: Go To 5
5. (K31) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO EXTERNAL VOLTAGE
Measure the voltage between the (K31) FCA return circuit in the FCA harness connector and battery negative.
Q: Is the voltage greater than 1 volts?
YES: Repair the (K31) FCA return circuit shorted to external voltage. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Go To 6
6. (K31) FCA RETURN CIRCUIT SHORTED TO (K181) FCA DRIVER CIRCUIT
Measure the Resistance between the return circuit in the FCA harness connector and Driver circuit.
Q: Is the resistance less than 10 Ohms?
YES: Repair the (K31) FCA Return circuit shorted to (K181) FCA Driver circuit. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Go To 7
7. (K181) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO GROUND
Measure the resistance between the (K181) FCA driver circuit in the FCA harness connector and battery negative.
Q: Is the resistance less than 10 Ohms?
YES: Repair the (K181) FCA driver circuit shorted to ground. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Go To 8
8. (K181) FUEL CONTROL ACTUATOR DRIVER CIRCUIT SHORTED TO ANOTHER CIRCUIT
Measure the resistance between the (K181) FCA driver circuit in the ECM harness connector and all other circuits in the ECM connectors.
Q: Is the resistance less than 10 Ohms?
NO: Go To 9
YES: Repair the (K181) FCA driver circuit shorted to another circuit. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
9. (K31) FUEL CONTROL ACTUATOR RETURN CIRCUIT SHORTED TO ANOTHER CIRCUIT
Measure the resistance between the (K31) FCA Return circuit in the ECM harness connector and all other circuits in the ECM connectors.8
Q: Is the resistance less than 10 Ohms?
NO: Go To 10
YES: Repair the (K31) FCA Return circuit shorted to another circuit. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
10. 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.
Q: Did the light flash brightly?
YES: Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure).
NO: Replace the ECM. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1