Glow Plug/Heater Circuit 'A' Malfunction
The P0380 code indicates a fault in the glow plug or heater circuit for cylinder 'A' (typically the first cylinder). Glow plugs are used in diesel engines to preheat the combustion chamber for cold starts. This code is set when the powertrain control module (PCM) detects an open or short circuit in the glow plug circuit, or when the glow plug resistance is out of specification. Common causes include a failed glow plug, a blown fuse, a faulty glow plug relay, or wiring issues. Symptoms may include hard starting in cold weather, excessive smoke, and a check engine light.
01. Most Common Causes
- Failed glow plug
- Blown fuse or faulty relay
- Open or shorted wiring in the glow plug circuit
- Faulty PCM (rare)
02. Symptoms You Will Notice
- Hard starting in cold weather
- Excessive white or gray smoke on startup
- Check engine light illuminated
- Rough idle or misfire until engine warms up
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Visually inspect glow plug wiring and connectors for damage or corrosion.
Step 3: Test glow plug resistance with a multimeter (typically 0.5-2 ohms).
Step 4: Check glow plug relay and fuse operation.
Step 5: If all else is fine, test the PCM output to the glow plug circuit.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
You can drive, but starting may be difficult in cold weather, and unburned fuel can damage the catalytic converter. It's best to repair promptly.
How much does it cost to fix?▼
Typically $50-$150 for a single glow plug replacement, including parts and labor. Costs vary by vehicle and location.