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Fuel Pump Electrical Circuit Diagnosis (Without FPCM)




Fuel Pump Electrical Circuit Diagnosis (Without FPCM)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions)provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within 2 seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.

Diagnostic Aids

The following conditions may cause the fuel pump fuse to open:

* The fuse is faulty.
* There is an intermittent short to ground in the supply voltage circuit of the fuel pump.
* The fuel pump has an intermittent internal condition.

Reference Information
Schematic Reference

Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool information
Special Tools

J 43244 Relay Puller Pliers

Circuit/System Verification

Important: An open or a short to voltage in the control circuit will cause both the Ckt. Open Test Status and the Ckt. Short Volts Test Status parameters to display Fault.


Ignition ON, command the fuel pump relay ON and OFF with a scan tool while observing the following control circuit status parameters:

* Fuel Pump Relay Ckt. Short Gnd Test Status
* Fuel Pump Relay Ckt. Open Test Status
* Fuel Pump Relay Ckt. Short Volts Test Status

Each parameter should toggle between OK and Not Run or Not Run and OK.

Circuit/System Testing

1. Ignition OFF, disconnect the fuel pump relay.
2. Ignition ON, verify that a test lamp illuminates between the ground circuit terminal and B+.

• If the test lamp does not illuminate, test the ground circuit for a short to voltage or an open/high resistance.

3. Verify that a test lamp does not illuminate between the ground circuit terminal and the control circuit terminal.

• If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Remove the test lamp.
5. Command the fuel pump relay ON with a scan tool. Verify the scan tool fuel pump relay Ckt. Short Grnd Test Status parameter is OK.

• If not the specified value, test the fuel pump relay control circuit for a short to ground. If the circuit tests normal, replace the ECM.

6. Install a 3A fused jumper wire between the fuel pump relay control circuit terminal and the ground circuit terminal. Command the fuel pump ON with a scan tool. Verify the scan tool fuel pump relay Ckt. Short Grnd Test Status parameter is Fault.

• If not the specified value, test the fuel pump relay control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

7. Inspect the fuel pump fuse.

• If the fuel pump fuse is open, test for the following conditions:

* A short to ground in the relay switch B+ circuit
* A short to ground in the supply voltage circuit of the fuel pump

• If the above circuits test normal, replace the fuel tank module.

8. Verify that a test light illuminates between the B+ circuit and ground.

• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

9. Connect a 15 A fused jumper wire between the B+ circuit and the supply voltage circuit of the fuel pump. Verify the fuel pup is activated.

• If the fuel pump does not activate, test for the following conditions:

* An open/high resistance in the supply voltage circuit of the fuel pump
* An open/high resistance in the ground circuit of the fuel pump

• If the above circuits test normal, replace the fuel tank module.

10. If all circuits test normal, test or replace the fuel pump relay.

Repair Instructions

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

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* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning)for ECM replacement, setup, and programming

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