P0678

Cylinder 8 Glow Plug Circuit/Open

Q: Is it safe to drive with P0678?

Usually yes once running, but expect hard cold starts and rough warm-up. Repair it before cold weather to avoid no-starts.

Q: Can I just clear P0678?

It returns on the next cold start until the failed glow plug or open circuit is repaired. Clearing only resets the light.

Glow plugs (diesel) Generic OBD-II High

What it means

P0678 is a diesel code meaning the control module detected an open (broken) circuit for cylinder 8's glow plug. Glow plugs preheat the combustion chamber for cold starting, so a failed plug or broken wire here shows up mainly 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 cold running; a warm diesel will normally still run on the remaining cylinders.

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

Difficulty starting, especially in cold weather (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 warning light on

Common causes

Most likely first

Failed cylinder 8 glow plug (open circuit)Likely
Open or broken wiring in the cylinder 8 glow plug circuitCommon
Loose or corroded electrical connector at the glow plugCommon
Faulty glow plug control moduleLess often

How to diagnose & fix

Work through it in order

Scan and confirm the code is for cylinder 8, and read freeze-frame data.
Inspect the cylinder 8 glow plug wiring and connector for an open, breakage, or corrosion.
Measure the glow plug's resistance; an open (infinite) reading means the plug has failed — replace it.
Verify the glow plug control module is powering the circuit before replacing it.
Repair, clear the code, and do a cold start to confirm the fix.

FAQ

Quick answers

Is it safe to drive with P0678?+

Usually yes once running, but expect hard cold starts and rough warm-up. Repair it before cold weather to avoid no-starts.

Can I just clear P0678?+

It returns on the next cold start until the failed glow plug or open circuit is repaired. Clearing only resets the light.

Read & clear P0678 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