Cylinder 7 Glow Plug Control Circuit High
The P068D code indicates that the powertrain control module (PCM) has detected a high voltage condition in the glow plug control circuit for cylinder 7. This typically means the circuit has excessive resistance or a short to voltage, preventing the glow plug from operating correctly. The glow plug system is critical for cold starts in diesel engines, and a fault can cause hard starting, misfires, and increased emissions.
1. Most Common Causes
- Faulty glow plug in cylinder 7
- 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
- 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: Scan for codes and record freeze frame data.
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; compare to specifications (typically 0.5-2 ohms).
Step 4: Check for voltage at the glow plug connector with key on; should be battery voltage.
Step 5: Test the glow plug control module output for cylinder 7.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code, as it can cause hard starting and potential engine damage if the glow plug fails completely.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for a single glow plug replacement, including parts and labor. Wiring repairs may add to the cost.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.