P066E

Cylinder 3 Glow Plug Control Circuit Low

Q: 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.

Q: 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.

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.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear P066E yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX