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 P064C 00: Glow Plug Control Module Control Circuit Malfunction
DTC P064C 04: Glow Plug Control Module Control Circuit Open
DTC P064C 54: Glow Plug Control Module High Temperature

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
B+ | P064C 04, P0380 00 | P064C 04, P0380 00 | P0380 00 | P0380 00
Ignition | P0380 00 | P0380 00 | P0380 00 | P0380 00
Control | P064C 00, P064C 54 | P064C 00 | P064C 00 | P0380 00, P064C 54
Ground | -- | -- | -- | P0380 00

### Circuit/System Description

The glow plug control module 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 control module within a wide range to suit the engine pre heating requirements. The ECM controls the glow plug control 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

• | The ignition is ON.

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

• | 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 s.

### Action Taken When the DTC Sets

DTC P064C is a Type C DTCs.

### Conditions for Clearing the DTC

DTC P064C is a Type C DTCs.

### 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 P064C 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 X1 at the K34 Glow Plug Control Module (GPCM).
2. Test for less than 5 Ω between the ground circuit terminal 3 (X1) and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the B+ circuit terminal 5 (X1) and ground.

⇒ | If the test lamp is OFF, test the B+ circuit for a short to ground or an open/high resistance.

4. Ignition ON, connect a test lamp between the ignition circuit terminal 4 (X1) and ground.

⇒ | If the test lamp is OFF, test the ignition circuit for a short to ground or an open/high resistance.

5. Test for less than 0.3 V between the control circuit terminal 2 (X1) and ground.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage.

6. Ignition OFF, disconnect the harness connector X2 at the K20 Engine Control Module (ECM).
7. Test for greater than 500 kΩ between the K34 Glow Plug Control Module (GPCM) control circuit terminal 2 (X1) and ground.

⇒ | If less than the specified range, test the signal circuit for a short to ground.

8. Test for less than 5 Ω between the control circuit terminal 2 (X1) at the K34 Glow Plug Control Module (GPCM) harness connector and terminal 42 (X2) at the K20 Engine Control Module (ECM) harness connector.

⇒ | If greater than the specified range, test the signal circuit for an open/high resistance.

9. If the circuit tests normal, replace the K34 Glow Plug Control Module (GPCM).
10. Verify the DTC does not reset.

⇒ | If DTC is set, replace the K20 Engine Control Module (ECM).

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Glow Plug Control Module Replacement for glow plug control module replacement

• | Engine Control Module Replacement for ECM replacement, setup, and programming