VIN L

Fuel Pump Electrical Circuit Diagnosis

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.

Circuit/System Description

The engine control module (ECM) provides ignition voltage to the fuel pump relay control circuit whenever the engine is cranking or running. The ECM enables the fuel pump relay as long as the engine is cranking or running, and crank sensor reference pulses are received.

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 End Views By Name)
Description and Operation

Fuel System Description (Fuel System Description)
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

Ignition ON, command the fuel pump relay ON and OFF with a scan tool. You should hear and feel a click when you command the fuel pump relay ON and OFF.

Circuit/System Testing

1. Ignition OFF, the fuel pump should not be running.

• If the fuel pump runs continuously, test for a short to voltage. If the circuit tests normal, replace the KR107 fuel pump relay.

2. Ignition OFF, remove the fuel pump relay from the electrical center with the J 43244.
3. Test for less than 5 ohm between the ground circuit terminal 85 and ground.

• If greater than the specified range, repair the ground circuit for an open/high resistance.

4. Ignition ON, verify a test lamp illuminates between the relay Battery Positive Voltage circuit terminal 30 and ground.

• If the test lamp does not illuminate, repair the Battery Positive Voltage circuit for a short to ground or an open/high resistance. Replace the fuse if necessary.

5. Connect a 15 A fused jumper wire between the relay Battery Positive Voltage circuit terminal 30 and the Fuel Pump Supply Voltage circuit terminal 87. The fuel pump should turn ON.

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

* An open/high resistance in the Fuel Pump Supply Voltage circuit
* An open/high resistance in the ground circuit

• If the above circuits test normal, replace the G12 fuel pump.

6. Ignition OFF, connect a test lamp between the Fuel Pump Primary Relay Control circuit terminal 86 and ground.
7. Ignition ON, command the fuel pump relay ON and OFF with a scan tool. The test lamp should turn ON and OFF with each command.

• If the test lamp is always ON, test the Fuel Pump Primary Relay Control circuit for a short to voltage. If the circuit tests normal, replace the K20 engine control module.

• If the test lamp is always OFF, test the Fuel Pump Primary Relay Control circuit for a short to ground or an open/high resistance. If circuit tests normal, replace the K20 engine control module.

8. If all circuits test normal, replace the KR107 fuel pump relay.

Component Testing

1. Ignition OFF, remove the fuel pump relay from the electrical center with the J 43244.
2. Test for 70-110 ohm between terminals 85 and 86.

• If not within the specified range, replace the KR107 fuel pump relay.

3. Test for infinite resistance between the following terminals:

* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87

• If not the specified value, replace the KR107 fuel pump relay.

4. Install a 20 A fused jumper wire between terminal 85 and 12 V. Install a jumper wire between terminal 86 and ground. Test for less than 2 ohm between terminals 30 and 87.

• If greater than the specified range, replace the KR107 fuel pump relay.

Repair Instructions

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