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 P2687 01: Fuel Heater Relay Control Circuit Short to Battery
DTC P2687 02: Fuel Heater Relay Control Circuit Short to Ground
DTC P2687 04: Fuel Heater Relay Control Circuit Open
DTC P2687 54: Fuel Heater Relay Control Circuit High Temperature

### Circuit/System Description

Ignition voltage is supplied to the coil side of the fuel heater relay whenever the ignition is ON. The engine control module (ECM) provides a ground to control the fuel heater relay. When the ECM is commanding the fuel heater ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding the fuel heater OFF, the voltage of the control circuit should be high, near battery voltage.

### Conditions for Running the DTC

• | The ignition is ON.

• | The ignition voltage is less than 16.5 volts.

• | The DTC runs continuously once the above conditions are met

### Conditions for Setting the DTC

#### P2687 01

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

#### P2687 02

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

#### P2687 04

The ECM detects the fuel heater relay control circuit is open for more than 1 second.

#### P2687 54

The control module detects the fuel heater relay control circuit temperature is too high for more than 1 second.

### Action Taken When the DTC Sets

DTC P2687 is a Type C DTC.

### Conditions for Clearing the DTC

DTC P2687 is a Type C DTC.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

1. Ignition ON, command the Fuel Heater Relay ON and OFF with a scan tool. You should hear and feel an audible click.
2. 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 Data List.

### Circuit/System Testing

1. Ignition OFF, disconnect the fuel heater relay from the underhood auxiliary fuseblock.
2. Connect a test lamp between the control circuit terminal 86 and B+.
3. Ignition ON, command the fuel heater 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 ground. If the circuit tests normal, replace the ECM.

⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage 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 ignition voltage circuit terminal 85.
5. Ignition ON, command the fuel heater 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 ignition voltage circuit for an open/high resistance.

6. If all circuits test normal, test or replace the fuel heater relay.

### Component Testing

1. Test for 70-110 ohms of resistance between terminals 85 and 86.

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

2. Test for infinite resistance between the following terminals:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

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

3. 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 fuel pump relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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