P0251 CP3 PUMP REGULATOR CONTROL

When Monitored and Set Condition:

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

• INTERMITTENT CONDITION
• FUEL CONTROL ACTUATOR
• (K31) RETURN CIRCUIT OPEN FROM FCA TO ECM
• (K65) 5-VOLT SUPPLY CIRCUIT OPEN FROM FCA TO ECM
• (K65) 5-VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE
• ECM

DIAGNOSTIC PROCEDURE

NOTE: Refer to VERIFICATION TESTS for appropriate verification test procedures.

1. With the DRBIII®, record all freeze frame data and erase DTC's. With the DRBIII®, read DTCs. Is the DTC P0251 set?
   Yes --> Go To 2
   No --> Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure).
2. Disconnect the fuel control actuator (FCA). Check connectors - Clean/repair as necessary. Measure the resistance between the (K65) 5-volt supply circuit and (K31) return circuit of the FCA. Is the resistance between 2.8 and 4.0 ohms?
   Yes --> Go To 3
   No --> Replace the fuel control actuator (FCA).
3. Disconnect the ECM harness connector. Check connectors - Clean/repair as necessary. Measure the resistance of the (K31) return circuit between the FCA and the ECM connector. Is the resistance less than 10 Ohms?
   Yes --> Go To 4
   No --> Repair or replace the engine wiring harness.
4. Measure the resistance of the (K65) 5-volt supply circuit between the FCA and the ECM connector. Is the resistance less than 10 Ohms?
   Yes --> Go To 5
   No --> Repair or replace the engine wiring harness.
5. Turn the ignition off. Measure the voltage between the (K65) 5-volt supply circuit in the electronic fuel control actuator connector and battery negative. Is the voltage greater than 1 volts?
   Yes --> Repair the (K65) 5-volt supply (K65) circuit shorted to voltage.
   No --> Go To 6
6. Reconnect the ECM harness connectors. Ignition on, engine not running. With the DRBIII®, erase DTCs. Monitor with the DRBIII® while connecting a jumper wire between the (K65) 5-volt supply and (K31) return circuits in the FCA connector. Did the DTC return?
   Yes --> Replace the ECM.
   No --> Test Complete.