GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

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

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Battery Voltage - Relay Switch

*

**

--

--

Ignition 1 Voltage - Relay Coil

P1230

P1230

P0563

--

Fuel Pump Supply Voltage

*

**

***

--

Fuel Pump Relay Control

P1230

P1230

P1231

--

Fuel Pump Ground

--

**

--

--

* The fuel pump fuse opens and the engine cranks but does not run.

** The engine cranks but does not run.

*** The fuel pump operates continuously and the battery will discharge.

Circuit/System Description

The engine control module (ECM) provides a ground 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 Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 43244 Relay Puller Pliers

Circuit/System Verification

  1. Ignition ON, observe the DTC information with a scan tool. DTCs P1230 and P1231 should not set.
  2. If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.
  3. Command the fuel pump relay ON with a scan tool. You should hear the fuel pump operate for 3-5 seconds and then turn OFF.
  4. 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 running.
  2. If the fuel pump runs continuously, test the relay switch supply circuit for a short to voltage. If the circuit tests normal, replace the fuel pump relay.
  3. Test the fuel pump fuse. The fuse should not be open.
  4. If the fuel pump fuse is open, test the relay switch supply circuit for a short to ground. If the circuit tests normal, replace the fuel pump.
  5. Ignition OFF, remove the fuel pump relay from the electrical center with the J 43244 .
  6. Ignition ON, test for battery voltage between the relay switch B+ voltage circuit terminal 30 and ground.
  7. If less than B+, repair the relay switch B+ voltage circuit for an open/high resistance.
  8. Connect a 15A fused jumper wire between the relay switch B+ circuit terminal 30 and the relay switch supply circuit terminal 87. The fuel pump should turn ON.
  9. If the fuel pump does not turn ON, test for the following conditions:
    • An open/high resistance in the relay switch supply circuit
    • An open/high resistance in the ground circuit of the fuel pump
    If the circuits test normal, replace the fuel pump.
  10. If all circuits test normal, test or replace the fuel pump relay.

Component Testing

  1. Ignition OFF, remove the fuel pump relay from the electrical center with the J 43244 relay puller pliers.
  2. Test for 70-110 ohms between terminals 85 and 86.
  3. If not within the specified range, replace the fuel pump relay.
  4. Test for infinite resistance between the following terminals:
  5. • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
    If not the specified value, replace the fuel pump relay.
  6. Install a 20A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.
  7. If greater than the specified range, replace the fuel pump relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Relay Replacement