Cylinder 12 Glow Plug Circuit Malfunction
The P0682 code indicates a fault in the glow plug circuit for cylinder 12. Glow plugs are used in diesel engines to preheat the combustion chambers for cold starts. This code is set when the powertrain control module (PCM) detects an abnormal voltage or resistance in the glow plug circuit for cylinder 12, which can prevent proper heating and cause hard starting, misfires, or increased emissions.
01. Most Common Causes
- Faulty glow plug in cylinder 12
- Open or shorted wiring in the glow plug circuit
- Failed glow plug relay or control module
- Corroded or loose electrical connector at the glow plug
02. Symptoms You Will Notice
- Hard starting, especially in cold weather
- Engine misfire or rough idle
- Check Engine Light illuminated
- Excessive white smoke from exhaust on startup
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for related codes.
Step 2: Visually inspect the glow plug wiring and connector for cylinder 12 for damage or corrosion.
Step 3: Measure resistance of the glow plug for cylinder 12; compare to specifications (typically 0.5-2 ohms).
Step 4: Test voltage supply to the glow plug circuit with key on; should be battery voltage.
Step 5: Check the glow plug relay and fuse for proper operation.
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, especially in cold weather, as it can cause hard starting, poor engine performance, and potential damage to the catalytic converter from unburned fuel.
How much does it cost to fix?▼
The cost to fix P0682 typically ranges from $150 to $400, depending on whether the glow plug itself needs replacement (around $50-$150 for parts and labor) or if wiring or relay repairs are needed.