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 provide 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 | 1 | 2 | -- | --
Ignition 1 Voltage - Relay Coil | P0628 | P0628 | P0563 | --
Fuel Pump Supply Voltage | 1 | 2 | 3 | --
Fuel Pump Relay Control | P0628 | P0628 | P0629 | --
Fuel Pump Ground | -- | 2 | -- | --

1. The fuel pump fuse opens and the engine cranks but does not run.
2. The engine cranks but does not run.
3. 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

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls Connector End Views

#### Description and Operation

Fuel System Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

#### Special Tools Required

J 43244 Relay Puller Pliers

### Circuit/System Verification

1. With the ignition ON, observe the DTC information with a scan tool. DTCs P0628 and P0629 should not be set.

⇒ | If the DTCs are 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. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

### 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 with the J 43244 relay puller pliers .

Important: The test lamp is used to load the circuit and may not illuminate.

4. Connect a test lamp between the battery positive (B+) voltage circuit of the fuel pump relay and ground.
5. Ignition ON, load test for battery voltage between the B+ voltage circuit of the fuel pump relay and ground.

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

6. Connect a 15-amp 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.

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

### Component Testing

1. Measure for 70-110 ohms of resistance between terminals 85 and 86 of the fuel pump relay.

⇒ | If the resistance is not within the specified range, replace the fuel pump relay.

2. Measure 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 continuity is detected, replace the fuel pump relay.

3. Connect a 20-amp fused jumper wire from the positive terminal of the battery to relay terminal 85. Connect a jumper wire from the negative terminal of the battery to relay terminal 86. Measure for less than 2 ohms between terminals 30 and 87 of the relay.

⇒ | If the resistance measures more than 2 ohms, replace the fuel pump relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

• | Fuel Pump Replacement