Glow Plug Control Module Circuit High Voltage
The P0384 code indicates that the powertrain control module (PCM) has detected a high voltage condition in the glow plug control module circuit. This circuit controls the glow plugs used to preheat the combustion chamber in diesel engines for cold starts. A high voltage reading suggests a short to power, faulty control module, or wiring issues, which can prevent proper glow plug operation and cause hard starting in cold weather.
1. Most Common Causes
- Not applicable: code reserved by SAE J2012 with no assigned fault definition
- May indicate outdated or incompatible scan tool software for the vehicle
- Proprietary manufacturer use not publicly documented
- Error in control module reading; verify with another diagnostic tool
2. Symptoms You Will Notice
- Hard starting, especially in cold weather
- Check Engine Light illuminated
- Excessive white smoke from exhaust on startup
- Rough idle or misfire until engine warms up
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the glow plug control module, wiring, and connectors for damage, corrosion, or loose connections.
Step 3: Test the voltage at the glow plug control module connector with a multimeter; compare to manufacturer specifications.
Step 4: Check for shorts to power by disconnecting the module and testing continuity between circuit pins and battery positive.
Step 5: If wiring is intact, test the glow plug control module per service manual procedures; replace if faulty.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances, especially in cold weather, as the glow plugs may not function, leading to hard starting and potential engine damage from excessive cranking.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, including parts and labor, depending on whether the control module or wiring needs replacement.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.