Fuel Pump: Testing and Inspection

Fuel Pump Electrical Circuit Diagnosis

Diagnostic Instructions

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

Circuit/System Description

The engine control module (ECM) provides a voltage to the coil side of the fuel pump relay. When the ignition switch is first turned ON, the ECM turns ON the fuel pump relay, which applies power to the fuel pump. The ECM enables the fuel pump relay as long as the engine is cranking or running, and crankshaft reference pulses are received. If no crankshaft reference pulses are received, the ECM turns OFF the fuel pump relay after about 3 seconds.

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 (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)

Scan Tool Reference

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

J 43244 Relay Puller Pliers

Circuit/System Verification

1. Ignition ON, command the fuel pump relay ON with a scan tool. You should hear the fuel pump operate for 2-3 seconds and then turn OFF.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

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

• If the fuel pump operates continuously, test for a short to voltage in supply voltage circuit of the fuel pump. If the circuit/connections test normal, replace the fuel pump relay.

2. Test the fuel pump fuse. The fuse should not be open.

• If the fuel pump fuse is open, test for a short to ground in the supply voltage circuit of the fuel pump. If the circuit/connections test normal, replace the fuel pump.

3. Ignition OFF, remove the fuel pump relay from the electrical center.
4. Ignition ON, test for battery voltage between the B+ voltage circuit of the fuel pump relay and ground.

• If less than B+, test the B+ voltage circuit of the fuel pump relay for an open/high resistance.

5. Connect a 15 A fused jumper wire between the B+ circuit of the fuel pump relay and the supply voltage circuit of the fuel pump. The fuel pump should operate.

• If the fuel pump does not operate, 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 circuit/connections test normal, replace the fuel pump.

6. If all circuit/connections test normal, test or replace the fuel pump relay.

Component Testing

1. Test for 110-150 ohm between terminals 1 and 2 of the fuel pump relay.

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

2. Measure the resistance between the terminals of the fuel pump relay listed below. The DMM should display O.L.

* 3 and 2
* 3 and 5
* 3 and 1
* 1 and 5

• If less than the specified value, replace the fuel pump relay.

3. Connect a 15 A fused jumper wire from the positive terminal of the battery to relay terminal 1. Connect a jumper wire from the negative terminal of the battery to relay terminal 2. Test for less than 2 ohm between terminals 3 and 5 of the relay.

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

Repair Instructions

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

* Primary Fuel Tank Module Replacement (Primary Fuel Tank Module Replacement)
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))