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.

### DTC Descriptors

DTC P0627 01: Fuel Pump Relay Control Circuit Short to Battery
DTC P0627 02: Fuel Pump Relay Control Circuit Short to Ground
DTC P0627 04: Fuel Pump Relay Control Circuit Open
DTC P0627 54: Fuel Pump Relay Control Circuit High Temperature

### Circuit/System Description

The engine control module (ECM) provides ignition voltage to the coil side of the fuel pump relay whenever the engine is cranking or running. The control module enables the fuel pump relay as long as the engine is cranking or running, and ignition system reference pulses are received. If no ignition system reference pulses are received, the control module turns OFF the fuel pump. The fuel pump relay control circuit is equipped with a feedback circuit that is pulled up to voltage within the ECM. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.

### Conditions for Running the DTC

#### P0627 01 and P0627 54

• | The ignition is ON, or the engine is running.

• | The power stage is active.

• | The DTCs run continuously once the above conditions are met

#### P0627 02 and P0627 04

• | The ignition is ON.

• | The power stage is not active.

• | The DTCs run continuously once the above conditions are met

### Conditions for Setting the DTC

#### P0627 01

The ECM detects the fuel pump relay control circuit is shorted to battery for greater than 1 second.

#### P0627 02

The ECM detects the fuel pump relay control circuit is shorted to ground for greater than 1 second.

#### P0627 04

The ECM detects the fuel pump relay control circuit is open for greater than 1 second.

#### P0627 54

The control module detects that the fuel pump relay control circuit temperature is too high for greater than 1 second.

### Action Taken When the DTC Sets

DTC P0627 is a Type C DTC.

### Conditions for Clearing the DTC

DTC P0627 is a Type C DTC.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### 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

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, command the Fuel Pump Relay ON and OFF with a scan tool. You should hear and feel an audible click.
2. 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, disconnect the fuel pump relay.
2. Connect a test lamp between the control circuit terminal 86 and ground.
3. Ignition ON, command the fuel pump ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | 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 the circuit tests normal, replace the ECM.

4. Ignition OFF, connect a test lamp between the control circuit terminal 86 and the ground circuit terminal 87.
5. Ignition ON, command the fuel pump ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp is always OFF, repair the ground circuit for an open/high resistance.

6. 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:

• | 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 12 volts. 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.

Control Module References for engine control module replacement, setup, and programming