P066E
Cylinder 3 Glow Plug Control Circuit Low
Glow plugs (diesel)
Generic OBD-II
High
What it means
P066E is a diesel code: the control module detected low voltage or a short to ground on the circuit that switches cylinder 3's glow plug. Glow plugs preheat the combustion chamber for cold starting, so a fault here mainly shows up as hard cold starts and rough running until the engine warms.
High
Can I keep driving? Usually driveable, but expect hard cold starts and rough running until the engine warms up; one weak glow plug rarely stops a warm engine.
Common symptoms
What you'll notice
- Hard starting when cold (long crank)
- Rough running or a temporary miss until the engine warms up
- White or grey exhaust smoke on a cold start
- Check-engine or glow-plug (coil) warning light on
Common causes
Most likely first
- Faulty cylinder 3 glow plug (open or shorted internally)Likely
- Short to ground or damaged wiring in the cylinder 3 glow plug control circuitCommon
- Corroded or loose connector at the glow plug or control moduleCommon
- Faulty glow plug control moduleLess often
How to diagnose & fix
Work through it in order
- Scan and confirm the code points to cylinder 3, and read freeze-frame data.
- Inspect the cylinder 3 glow plug wiring and connector for a short to ground, chafing, or corrosion.
- Measure the glow plug's resistance and compare to spec; replace it if out of range.
- Check the glow plug control module and its power/ground before condemning it.
- Repair the fault, clear the code, and cold-start the engine to confirm it's resolved.
FAQ
Quick answers
Is it safe to drive with P066E?+
Usually yes for short trips, but cold starts will be hard and the engine may run rough until warm. Fix it before winter to avoid no-starts.
Can I just clear P066E?+
It will come back on the next cold start until the glow plug or its circuit is repaired. Clearing only resets the light temporarily.
Related codes
Often seen with P066E
Read & clear P066E 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