P0671
Cylinder 1 Glow Plug Circuit/Open
Diesel glow plug / preheat
Generic OBD-II
High
What it means
P0671 is a diesel-engine code showing an open circuit in the glow plug for cylinder 1. Glow plugs preheat the cylinders so the engine fires easily when cold, so with this fault you will notice hard cold starts and rough running until the engine warms up. The engine still runs, but the cylinder 1 glow plug or its wiring needs attention.
High
Can I keep driving? The engine still runs, but on a diesel it may be hard to start and run rough when cold until the cylinder 1 glow plug circuit is repaired.
Common symptoms
What you'll notice
- Hard starting, especially in cold weather
- Check-engine (or glow plug) light on
- Rough running and misfire-like shudder when the engine is cold
- White or grey smoke from the exhaust on a cold start
Common causes
Most likely first
- Failed glow plug on cylinder 1 (open element)Likely
- Open or broken wiring between the glow plug module and cylinder 1Common
- Corroded or loose connector at the glow plugCommon
- Glow plug control module fault affecting the cylinder 1 outputLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check for glow plug codes on other cylinders to narrow the fault.
- Measure the resistance of the cylinder 1 glow plug — an open reading means the plug has failed.
- Inspect the wiring and connector from the glow plug module to cylinder 1 for breaks or corrosion.
- Replace the failed glow plug or repair the circuit, then clear and re-test on a cold start.
FAQ
Quick answers
Is it safe to drive with P0671?+
Yes once running, but cold starts get harder and the engine runs rough until warm, so repair it before winter.
Can I just clear P0671?+
It will return on the next cold start until the cylinder 1 glow plug or its circuit is fixed.
Related codes
Often seen with P0671
Read & clear P0671 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