P068C
Cylinder 7 Glow Plug Control Circuit Low
Glow plug / diesel preheat
Generic OBD-II
High
What it means
P068C is a diesel code meaning the ECM has detected a low-voltage (usually short-to-ground) fault in the glow plug control circuit for cylinder 7. Glow plugs pre-heat the cylinder for cold starting, so the main symptoms are hard cold starts and rough, smoky running until the engine warms up.
High
Can I keep driving? You can usually drive once warm, but expect hard cold starts and rough cold running until the glow plug circuit is repaired.
Common symptoms
What you'll notice
- Hard or slow starting when cold
- Rough idle and white smoke on a cold start until warm
- Glow plug (coil) warning light or check-engine light on
- Reduced power in cold weather
Common causes
Most likely first
- Shorted glow plug on cylinder 7Likely
- Glow plug wiring shorted to ground (low-voltage fault)Common
- Corroded or loose electrical connectorCommon
- Faulty glow plug control moduleLess often
- Faulty ECM/PCM driver (less common)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the fault is on cylinder 7.
- Measure the cylinder 7 glow plug resistance — a shorted plug reads very low and needs replacing.
- Inspect the harness for a short to ground and check the connector for corrosion.
- Check the glow plug control module output and its power/ground.
- Repair the short, clear the code, and retest a cold start.
FAQ
Quick answers
Is it safe to drive with P068C?+
Usually yes once warm, but cold starts will be hard and it may run rough and smoke. It's not an emergency, but fix it before cold weather.
Can I just clear P068C?+
It comes back once the ECM re-tests the circuit. The shorted plug or wiring has to be repaired for the code to stay away.
Related codes
Often seen with P068C
Read & clear P068C yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX