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 P0380 00: Glow Plug Feedback Circuit Malfunction
DTC P0383 02: Glow Plug Feedback Circuit Low Voltage
DTC P0384 00: Glow Plug Feedback Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
B+ | P0380 00 | P0380 00 | P0380 00 | P0380 00
Ignition | P0380 00 | P0380 00 | P0380 00 | P0380 00
Signal | P0383 02 | P0383 02 | P0384 00 | P0380 00
Ground | -- | -- | -- | P0380 00

### 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

#### P0380 00

• | 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.

#### P0383 02 or P0384 00

• | 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 P0380, P0383 and P0384 are Type C DTCs.

### Conditions for Clearing the DTC

DTC P0380, P0383 and P0384 are 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 P0380, P0383 or P0384 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 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 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 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 signal circuit terminal 1 and ground.

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

6. Ignition OFF, disconnect the harness connector X1 at the K20 Engine Control Module (ECM).
7. Test for greater than 500 kΩ between the K34 Glow Plug Control Module (GPCM) signal circuit terminal 1 and ground.

⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

8. Test for less than 5 Ω between the signal circuit terminal 1 at the K34 Glow Plug Control Module (GPCM) harness connector and terminal 57 at the K20 Engine Control Module (ECM) harness connector.

⇒ | If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

9. If the circuit tests normal, replace the K34 Glow Plug Control Module (GPCM).

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Glow Plug Control Module Replacement

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