Fuel Pump Electrical Circuit Diagnosis

Fuel Pump Electrical Circuit Diagnosis

Diagnostic Instructions

* Perform theDiagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview)provide an overview of each diagnostic category.



Diagnostic Fault Information






Circuit/System Description

The engine control module (ECM) supplies voltage to the fuel pump flow control module (FPCM) when the ECM detects that the ignition is on. The voltage from the ECM to the FPCM remains active for two seconds, unless the engine is in crank or run. While this voltage is being received, the FPCM closes the ground switch of the fuel pump and also supplies a varying voltage to the fuel tank pump module in order to maintain the desired fuel rail pressure.


Reference Information
Schematic Reference

Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Fuel System Description (Fuel System Description)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool


Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the fuel pump.
2. Connect a test lamp between the control circuit terminal 1 and ground.
3. Ignition ON, command the fuel pump ON and OFF using a scan tool. The test lamp should turn ON and OFF as commanded.

• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the FPCM.


• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the FPCM.

4. Ignition OFF, connect a test lamp between the control circuit terminal 2 and the control circuit terminal 1.
5. Ignition ON, command the fuel pump ON using a scan tool. The test lamp should illuminate.

• If the test lamp does not illuminate, test the control circuit terminal 2 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the FPCM.

6. If all circuits test normal, replace the fuel tank fuel pump module.



Repair Instructions

Perform theDiagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Fuel Tank Fuel Pump Module Replacement (Service and Repair)
* Control Module References (Programming and Relearning)for FPCM replacement, setup, and programming