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 chamber for cold starts. This code is set when the powertrain control module (PCM) detects an open or short circuit in the glow plug or its wiring. A faulty glow plug, damaged wiring, or a failed glow plug control module can trigger this code, leading to hard starting, misfires, and increased emissions.
1. Most Common Causes
- Faulty glow plug in cylinder 12 (internal open circuit)
- Open, short-to-ground, or short-to-voltage in the wiring or connectors of the glow plug circuit for cylinder 12
- Defective glow plug control module (GPCM)
- Blown fuse or fusible link in the power supply circuit for glow plug 12
- Internal PCM failure (uncommon)
2. Symptoms You Will Notice
- Hard starting, especially in cold weather
- Engine misfire or rough idle after start
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for additional codes.
Step 2: Visually inspect the glow plug wiring and connector for cylinder 12 for damage or corrosion.
Step 3: Measure the resistance of the glow plug; it should be low (typically 0.5-2 ohms). Replace if open or shorted.
Step 4: Check the glow plug control module and relay for proper operation.
4. 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 and potential engine damage from incomplete combustion.
How much does it cost to fix?▼
The cost to fix a P0682 code typically ranges from $50 to $150, including parts (glow plug) and labor. If the control module needs replacement, costs can be higher.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.