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 greater than 1 second.

#### P2687 02

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

#### P2687 04

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

#### P2687 54

The control module detects the fuel heater relay control circuit temperature is too high for greater 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

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 heater 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 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 relay 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 K20 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 K20 ECM.

4. Ignition OFF, connect a test lamp between the control circuit terminal 86 and the ignition 1 voltage circuit terminal 85.
5. Ignition ON, command the fuel heater relay 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 1 voltage circuit for an open/high resistance.

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

### Component Testing

1. Ignition OFF, disconnect the fuel heater relay from the underhood auxiliary fuseblock.
2. Test for 70-110 Ω 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 20 A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 Ω 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