Fuel Pump Electrical Circuit Diagnosis
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 1-2 Shift Solenoid (SS) Valve (M30)
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 Control Module References for scan tool information
Special Tools
J 43244 - Relay Puller Pliers
Circuit/System Verification
1. Ignition ON.
2. 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.
• If Fuel Relay does not click
Refer to Circuit/System Testing.
• If Fuel Pump Relay clicks
3. All OK.
Circuit/System Testing
1. Ignition OFF.
2. 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 Fuel Pump Relay.
• If the Fuel Pump is not running
3. Ignition OFF.
4. Remove the Fuel Pump Relay from the electrical center with the J 43244 - relay puller pliers.
5. Test for less than 5 ohms between the ground circuit terminal 85 and ground.
• If greater than 5 ohms
Repair the ground circuit for an open/high resistance.
• If less than 5 ohms
6. Ignition ON.
7. 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.
• If test lamp illuminates
8. 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
1. Test for an open/high resistance in the Fuel Pump Supply Voltage circuit
• If an open/high resistance was found.
Repair as necessary
• If no open/high resistance was found.
2. Test for an open/high resistance in the ground circuit.
• If an open/high resistance was found.
Repair as necessary
• If no open/high resistance was found.
3. Replace the G12 Fuel Pump.
• If the Fuel Pump turns ON
9. Ignition OFF.
10. Connect a test lamp between the Fuel Pump Primary Relay Control circuit terminal 86 and ground.
11. Ignition ON.
12. 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
1. Test the Fuel Pump Primary Relay Control circuit for a short to voltage
• If a short to voltage was found.
Repair as necessary.
• If no short to voltage was found.
2. Replace the K20 Engine Control Module.
• If the test lamp is always OFF
1. Test the Fuel Pump Primary Relay Control circuit for a short to ground or an open/high resistance.
• If a short to ground or an open/high resistance was found.
Repair as necessary.
• If no short to ground or an open/high resistance was found.
• Replace the K20 Engine Control Module.
• If test lamp turns ON and OFF
13. Replace the Fuel Pump Relay.
Component Testing
1. Ignition OFF.
2. Remove the Fuel Pump Relay from the electrical center with the J 43244 - relay puller pliers.
3. Test for 70-110 ohms between terminals 85 and 86.
• If not within 70 to 110 ohms
Replace the Fuel Pump Relay.
• If within 70 to 110 ohms
4. Test for infinite resistance between the following terminals:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If not infinite resistance
Replace the Fuel Pump Relay.
• If infinite resistance
5. 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 ohms between terminals 30 and 87.
• If greater than 2 ohms
Replace the Fuel Pump Relay.
• If less than 2 ohms
6. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness) for Fuel Transfer Pump Relay replacement.
* Fuel Pump Replacement (Secondary) Service and RepairFuel Pump Replacement (Primary) Service and Repair for Fuel Transfer Pump replacement.
* Control Module References Control Module References for Engine Control Module replacement, setup, and programming.