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 is responsible for energizing the glow plug to aid cold starts in diesel engines. A low voltage reading suggests excessive resistance, a short to ground, or a faulty glow plug module, which can prevent the glow plug from heating properly, leading to hard starting, misfires, and increased emissions.
01. Most Common Causes
- Faulty glow plug in cylinder 7
- Open or shorted glow plug wiring harness
- Corroded or loose electrical connector at glow plug
- Failed glow plug control module or relay
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially in cold weather
- Rough idle or misfire on cylinder 7
- Reduced fuel economy and increased exhaust smoke
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data to confirm P068C and check for related codes.
Step 2: Visually inspect the glow plug wiring and connector for cylinder 7 for damage, corrosion, or looseness.
Step 3: Measure resistance of glow plug 7; compare to specification (typically 0.5-2 ohms). Replace if out of range.
Step 4: Test voltage at glow plug connector with key on; should be battery voltage. If low, check circuit back to control module.
04. Commonly Affected Makes
05. 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 may 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 typically ranges from $50 to $150 for a DIY glow plug replacement, or $150 to $400 if professional labor is required, depending on the vehicle and shop rates.