Fuel Pump Electrical Circuit Diagnosis. Chevrolet Joy 2008

For 1990-2009 cars

### 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 | P0628 | P0628 | P0563 | --
Fuel Pump Supply Voltage | * | ** | *** | --
Fuel Pump Relay Control | P0628 | P0628 | P0629 | --
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

#### Description and Operation

Fuel System Description

#### 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 P0628 and P0629 should not set.

⇒ | If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

2. Ignition ON, 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.
3. 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.

⇒ | If the fuel pump runs continuously, test the fuel pump supply circuit for a short to voltage. If the circuit tests normal, replace the fuel pump relay.

2. Ignition OFF, remove the fuel pump relay from the electrical center with the J 43244 relay puller pliers.
3. Ignition ON, verify a test lamp illuminates between the relay switch B+ circuit terminal 30 and ground.

⇒ | If the test lamp does not illuminate, repair the relay switch B+ circuit for a short to ground or an open/high resistance.

4. Install 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 operate.

⇒ | If the fuel pump does not run, test for the following conditions:

• | An open/high resistance in the relay switch supply circuit

• | An open/high resistance in the ground circuit

⇒ | If the above circuits test normal, replace the fuel pump.

5. Ignition OFF, connect a test lamp between the relay coil control circuit terminal 86 and the relay coil ignition 1 circuit terminal 85.
6. 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 control circuit for a short to voltage. If the circuit tests normal, replace the ECM.

⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If circuit tests normal, replace the ECM.

7. If all circuits test normal, test or replace the fuel pump relay.

### Component Testing

1. Ignition OFF, disconnect the fuel pump relay.
2. Test for 70-110 ohms of resistance between terminals 85 and 86.

⇒ | If not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals of the fuel pump relay:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If not the specified value, replace the relay.

4. Install a 20A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.

⇒ | If greater than the specified range, replace the relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

• | Fuel Pump Replacement