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Fuel Pump Electrical Circuit Diagnosis

Fuel Pump Electrical Circuit Diagnosis

Diagnostic Instructions


• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provide an overview of each diagnostic category.


Diagnostic Fault Information

Circuit Short to Ground Open or High Resistance Short to Voltage Signal Performance
Fuel Pump High Signal P0231 P023F P0232 P023F, P2635
Fuel Pump Low Signal - P023F - P023F, P2635


Circuit/System Description

The engine control module (ECM) supplies voltage to the fuel pump control module when the ECM detects that the ignition is on. The voltage from the ECM to the fuel pump control module remains active for two seconds, unless the engine is in crank or run. While this voltage is being received, the fuel pump control module 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 (3.0L (LF1)) Engine Controls Schematics (2.8L (LAU))

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel System Description (LF1) Fuel System Description (LAU or LY7)

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, command the fuel pump ON and OFF using the scan tool ECM output control. The fuel pump should turn on and off.

Circuit/System Testing


1. Ignition OFF, disconnect the harness connector at the G12 fuel pump.

2. Connect a test lamp between the control circuit terminal A and ground.

3. Ignition ON, command the G12 fuel pump ON and OFF using a scan tool ECM fuel pump output control. The test lamp should turn ON and OFF, as commanded.

4. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K27 fuel pump control module.

5. 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 K27 fuel pump control module.

6. Ignition OFF, connect a test lamp between the control circuit terminal A and the low reference circuit terminal B.

7. Ignition ON, command the G12 fuel pump ON using a scan tool. The test lamp should illuminate.

8. If the test lamp does not illuminate, test the low reference circuit terminal A for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K27 fuel pump control module.

9. If all circuits test normal, replace the G12 fuel pump.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for fuel pump control module replacement, setup, and programming