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 Descriptor

DTC P0655 01: Engine Coolant Temperature Indicator Control Circuit Shorted to Voltage
DTC P0655 02: Engine Coolant Temperature Indicator Control Circuit Shorted to Ground
DTC P0655 04: Engine Coolant Temperature Indicator Control Circuit Open
DTC P0655 54: Engine Coolant Temperature Indicator Control Circuit High Temperature

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Engine Coolant Temperature Lamp Voltage Supply | P0655 04 | P0655 04 | -- | --
Engine Coolant Temperature Lamp Control | P0655 02 | P0655 04 | P0655 01 | --

### Circuit/System Description

The engine coolant temperature indicator, is located on the instrument panel cluster (IPC). Ignition 1 voltage is supplied directly to the engine coolant temperature indicator. The engine control module (ECM) turns the engine coolant temperature indicator ON by grounding the control circuit.

### Conditions for Running the DTC

• | The engine is operating.

• | The ignition 1 voltage is between 7.5-16 volts.

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

### Conditions for Setting the DTC

The ECM detects the engine coolant temperature indicator control circuit is open or shorted to ground or voltage.

### Action Taken When the DTC Sets

DTC P0655 is a Type C DTC.

### Conditions for Clearing the DTC

DTC P0655 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. Engine idling, command the engine coolant temperature indicator ON and OFF with a scan tool. The indicator should turn ON and OFF.
2. Observe the DTC information with a scan tool. DTC P0655 should not set.
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. If any other indicators are inoperative on the P16 instrument panel cluster (IPC), refer to Symptoms - Displays and Gages.
2. Ignition OFF, disconnect the harness connector at the K20 ECM.
3. Ignition ON, the engine coolant temperature indicator should not illuminate.

⇒ | If the engine coolant temperature indicator illuminates, test the control circuit for a short to ground. If the circuit test normal, replace the P16 IPC.

4. Ignition ON, connect a 3 A fused jumper wire between the engine coolant temperature indicator control circuit terminal and ground. The engine coolant temperature indicator should illuminate.

⇒ | If the engine coolant temperature indicator does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit test normal, replace the P16 IPC.

⇒ | If the engine coolant temperature indicator illuminates, inspect for a poor connection or replace the K20 ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Instrument Cluster Replacement

• | Control Module References for ECM replacement, setup, and programming