P0677

Cylinder 7 Glow Plug Circuit/Open

Q: Is it safe to drive with P0677?

Usually yes once warm, but cold starts will be difficult and it may run rough and smoke. It's not an emergency, but fix it before cold weather.

Q: Can I just clear P0677?

It will come back the next time the ECM checks the glow plug circuit. The open plug or wire has to be fixed for the code to stay away.

Glow plug / diesel preheat Generic OBD-II High

What it means

P0677 is a diesel code meaning the ECM has found an open circuit in the glow plug for cylinder 7. Glow plugs pre-heat the combustion chamber for cold starting, so a single open plug mainly causes hard cold starts and rough, smoky running until the engine warms up — it does not affect a warm engine.

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.

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 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

Failed (open) glow plug on cylinder 7Likely
Open or shorted wiring/harness to the cylinder 7 glow plugCommon
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 — an open plug reads infinite and needs replacing.
Inspect the harness and connector for an open circuit or corrosion.
Check the glow plug control module output and its power/ground.
Repair the open, clear the code, and retest a cold start.

FAQ

Quick answers

Is it safe to drive with P0677?+

Usually yes once warm, but cold starts will be difficult and it may run rough and smoke. It's not an emergency, but fix it before cold weather.

Can I just clear P0677?+

It will come back the next time the ECM checks the glow plug circuit. The open plug or wire has to be fixed for the code to stay away.

Read & clear P0677 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