P06C9
Cylinder 5 Glow Plug Incorrect
Diesel glow plug / preheat
Generic OBD-II
High
What it means
P06C9 is a diesel code meaning the glow plug control module sees the cylinder 5 glow plug behaving incorrectly — its resistance or response is out of the expected range. This usually points to a weak or degraded glow plug or a poor connection. Because glow plugs only preheat for starting, the effects are hard cold starts, rough warm-up, and cold-start smoke.
High
Can I keep driving? Usually yes, but expect hard cold starts and rough cold running until the cylinder 5 glow plug circuit is repaired.
Common symptoms
What you'll notice
- Hard starting, especially in cold weather
- Rough idle or a miss until the engine warms up
- White or grey exhaust smoke on a cold start
- Check-engine or glow-plug warning light on
Common causes
Most likely first
- Cylinder 5 glow plug reading incorrectly (wrong resistance or weak element)Likely
- High-resistance or corroded connection at the glow plugCommon
- Chafed or partially shorted glow plug wiringCommon
- Faulty glow plug control moduleLess often
How to diagnose & fix
Work through it in order
- Scan and read freeze-frame to confirm the fault is on cylinder 5.
- Measure the cylinder 5 glow plug's resistance against the others and replace it if it reads wrong.
- Clean and inspect the glow plug connection and wiring for corrosion or high resistance.
- Check the glow plug control module output, then clear and re-test on a cold start.
FAQ
Quick answers
Is it safe to drive with P06C9?+
Generally yes in mild weather. A single out-of-spec glow plug mainly causes hard cold starting and rough warm-up; repair it before cold weather.
Can I just clear P06C9?+
It returns on the next cold start unless the glow plug or its connection is corrected.
Related codes
Often seen with P06C9
Read & clear P06C9 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