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 typically occurs when the voltage signal from the glow plug control module exceeds the manufacturer's specified range. The glow plug system is critical for cold starts in diesel engines, as it preheats the combustion chambers. A high voltage condition can be caused by a faulty glow plug control module, shorted wiring, or a defective PCM. This issue can lead to extended cranking, rough idle, and increased emissions.
01. Most Common Causes
- Faulty glow plug control module
- Shorted or damaged wiring in the glow plug circuit
- Corroded connectors or poor ground connections
- Defective PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially in cold weather
- Rough idle or misfire on cold start
- Excessive smoke from exhaust during startup
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for additional codes.
Step 2: Visually inspect the glow plug control module and wiring for damage, corrosion, or loose connections.
Step 3: Test the voltage supply and ground at the glow plug control module connector using a multimeter.
Step 4: If voltage is out of spec, repair or replace the wiring; if wiring is good, replace the glow plug control module.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code, as it can cause hard starting and potential damage to the glow plug system. In cold weather, the vehicle may not start at all.
How much does it cost to fix?▼
The cost to fix P0384 typically ranges from $150 to $400, including parts and labor. The glow plug control module itself costs $100-$250, and labor is around $50-$150.