Cylinder 8 Glow Plug Control Circuit High
The P068F code indicates that the powertrain control module (PCM) has detected a high voltage condition in the glow plug control circuit for cylinder 8. This typically means the circuit has excessive resistance or a short to voltage, preventing proper glow plug operation. In diesel engines, glow plugs preheat the combustion chamber for cold starts; a fault can cause hard starting, misfires, and increased emissions.
1. Most Common Causes
- Faulty glow plug in cylinder 8
- Open or shorted wiring in the glow plug circuit
- Corroded or damaged connector at the glow plug
- Failed glow plug control module or relay
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially in cold weather
- Rough idle or misfire on cylinder 8
- Reduced fuel economy
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the glow plug wiring and connector for cylinder 8 for damage or corrosion.
Step 3: Measure resistance of the glow plug; should be low (0.5-2 ohms). High resistance indicates a bad plug.
Step 4: Check for voltage at the glow plug connector with key on; should be battery voltage. If not, test the control circuit back to the module.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
You can drive short distances, but avoid cold starts and heavy loads. The engine may be hard to start and run poorly, potentially causing further damage.
How much does it cost to fix?▼
Typically $50-$150 for a single glow plug replacement, including parts and labor. Wiring repairs may add cost.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.