Volt

Fuel Pump Electrical Circuit Diagnosis

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.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

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

1. Vehicle OFF, disconnect the harness connector at the G12 fuel pump.
2. Connect a test lamp between the control circuit terminal 1 and ground.
3. Vehicle in Service Mode, 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.

⇒	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.

⇒	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.

4. Vehicle OFF, connect a test lamp between the control circuit terminal 1 and the low reference circuit terminal 2.
5. Vehicle in Service Mode, command the G12 fuel pump ON using a scan tool. The test lamp should illuminate.

⇒	If the test lamp does not illuminate, test the low reference circuit terminal 1 for a short-circuit to voltage or an open/high resistance. If the circuit tests normal, replace the K27 fuel pump control module.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.