Cylinder 7 Glow Plug Control Circuit Low
The P068C code indicates that the powertrain control module (PCM) has detected a low voltage condition in the glow plug control circuit for cylinder 7. This circuit controls the glow plug, which preheats the combustion chamber for easier cold starts in diesel engines. A low voltage reading suggests a short to ground, open circuit, or faulty component, potentially causing hard starting, misfires, or increased emissions.
1. Most Common Causes
- Faulty glow plug in cylinder 7
- Open or shorted glow plug wiring or connector
- Failed glow plug control module or relay
- Corrosion or damage in the glow plug circuit
2. Symptoms You Will Notice
- Hard starting, especially in cold weather
- Engine misfire or rough idle
- Check Engine Light illuminated
- Reduced fuel economy
3. 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 7 for damage or corrosion.
Step 3: Measure resistance of the glow plug; should be low (0.5-2 ohms). Replace if open or shorted.
Step 4: Test voltage at the glow plug connector with key on; should be battery voltage. If low, check relay and control module.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances, especially in cold weather, as it can cause hard starting, misfires, and potential damage to the engine or catalytic converter.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for a glow plug replacement, but can be higher if wiring or the control module needs repair.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.