P025D

P025D-FUEL PUMP MODULE CONTROL CIRCUIT HIGH

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





Theory of Operation

When the Powertrain Control Module (PCM) receives a 'Start' or 'Run' signal from the ignition; It energizes the Fuel Pump relay which sends a continuous 12 volt supply to the Fuel Pump Control Module (FPCM). The PCM also sends a control signal directly to the FPCM which regulates the Pulse Width Modulated (PWM) voltage that will be sent to the Fuel Pump Module. The PWM will vary from 10-100% depending on the input of the Fuel Rail Pressure sensor and other engine demands. The Powertrain Control Module (PCM) receives a Pulse Width Modulated (PWM) signal from the Fuel Pump Control Module (FPCM) representing the state of all inputs and outputs of the FPCM. This is a Constant Pressure Fuel system which means any Delta Pressure test performed on the Fuel Pump would show a continuous pressure (regardless of the changes in PWM). If a pressure sensor fails or other failures are present; The duty cycle goes to Limp mode (100%) to maintain fuel pressure.

- When Monitored:
Engine running. Battery voltage greater than 11.0 Volts.

- Set Conditions:
MIL code sets when the Fuel Pump Control Module (FPCM) detects a voltage on the FPCM Motor Feed circuit above the calibrated threshold. The PCM sets the code after the failure matures for 60 seconds.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. ACTIVE DTC

NOTE: If DTC P0627 is present, repair that DTC before proceeding with this test.

1. Ignition on, engine not running.
2. With the scan tool, select View DTCs.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition Test.

2. CHECK THE (N1) FPCM MOTOR FEED CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition on, engine off.
2. With the scan tool, begin the Variable Speed Fuel Pump Relay Actuation Test.
3. Disconnect the FPCM harness connector.
4. Measure the voltage on the (N1) FPCM Motor Feed circuit at the FPCM harness connector.

Is the voltage above battery voltage?

Yes

- Repair the (N1) FPCM Motor Feed circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

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