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 P0670 01: Glow Plug Control Module Control Circuit Short to Battery
DTC P0670 02: Glow Plug Control Module Control Circuit Short to Ground
DTC P0670 04: Glow Plug Control Module Control Circuit Open Circuit
DTC P0670 54: Glow Plug Control Module Control Circuit Temperature High

### Circuit/System Description

The glow plug controller is a solid state device which operates the glow plugs. The temperature and the power consumption is controlled between the engine control module (ECM) and the glow plug controller within a wide range to suit the engine's pre-heating requirements. The ECM controls the glow plug module with a pulse-width modulated (PWM) control circuit. The glow plug initial ON time will vary based on the system voltage and temperature. Lower temperatures cause longer ON times.

### Conditions for Running the DTC

#### P0670 01 or P0670 54

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

• | The ignition voltage is between 9-16 volts.

• | The DTCs run once per ignition cycle when the above conditions are met.

#### P0670 02 or P0670 44

• | The ignition is ON.

• | The ignition voltage is between 9-16 volts.

• | The DTCs run once per ignition cycle when the above conditions are met.

### Conditions for Setting the DTC

The ECM detects an open, short to ground, or a short to voltage on the glow plug module control circuit for greater than 0.5 seconds.

### Action Taken When the DTC Sets

DTC P0670 is a Type C DTC.

### Conditions for Clearing the DTC

DTC P0670 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, observe the DTC information with a scan tool. DTC P0670 should not set.
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 harness connector at the glow plug control module.
2. Ignition ON, test for greater than 10 volts between the glow plug control module control circuit terminal 10 and ground.

⇒ | If less than the specified range, test the control circuit for an open or a short to ground. If the circuit tests normal, replace the ECM.

3. Test the A/C frequency from the glow plug control module control circuit terminal 10. Command the glow plug control module ON with a scan tool. Verify the A/C frequency is between 30-35 Hz.

⇒ | If less than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.

⇒ | If greater than the specified range, test the control circuit for a high resistance. If the circuit tests normal, replace the ECM.

4. If the circuit tests normal, test or replace the glow plug control module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming