Fuel Pump Electrical Circuit Diagnosis
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.
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 (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
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
Note: 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. With the ignition OFF, remove the fuel pump relay from the rear electrical center using the J 43244 - Pliers.
2. With the ignition ON, engine OFF, probe the control circuit terminal 3 of the fuel pump relay with a test lamp that is connected to a ground. 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 does not turn ON and OFF, test for an open or a short to ground in the fuel pump relay control circuit, or a faulty engine control module (ECM).
• If the test lamp remains illuminated with each command, test for a short to voltage in the control circuit of the fuel pump relay, an intermittent or a poor connection at the ECM, or a faulty ECM.
3. Connect a test lamp between the control circuit terminal 3 of the fuel pump relay and the ground circuit terminal 4 of the fuel pump relay. Command the fuel pump relay ON and OFF with a scan tool.
• If the test lamp does not turn ON and OFF, repair the open or the high resistance in the ground circuit of the fuel pump relay.
• If the test lamp does turn ON and OFF, test for an intermittent and for a poor connection at the fuel pump relay, or a faulty fuel pump relay.
4. Inspect the fuel pump fuse.
• If the fuel pump fuse is open, test for a short to ground in the supply voltage circuit of the fuel pump, or a faulty fuel pump.
5. With the ignition ON, engine OFF, probe the battery positive voltage circuit terminal 1 of the fuel pump relay with a test lamp that is connected to a ground.
• If the test lamp does not illuminate, repair the open in the battery positive voltage circuit.
6. Connect a 15A fused jumper wire between the battery positive voltage circuit terminal 1 of the fuel pump relay and the supply voltage circuit terminal 5 of the fuel pump.
• If the fuel pump operates, test for an intermittent or poor connection at the fuel pump relay, or a faulty fuel pump relay.
• If the fuel pump does not operate, test for an open or high resistance in the supply voltage circuit of the fuel pump, an open or high resistance in the ground circuit of the fuel pump, an intermittent or poor connection at the fuel sender cover, or a faulty fuel sender.
7. 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.
* Fuel Sender Assembly Replacement (Service and Repair)
* 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