Engine and gearbox (P)
P0670: Glow Plug Control Module Circuit
The glow plug control module is not functioning correctly, which can affect the starting and running of a diesel engine, especially in cold conditions.
Checked by a licensed car technician · last reviewed 29 September 2026
Symptoms
- Hard starting in cold weather
- Rough idle after cold start
- Engine misfires when cold
Common causes
- Faulty glow plug controller
- Blown fuse
- Wiring harness fault
How to check it yourself
- Check the supply voltage to the module
- Inspect and replace any blown fuses
- Examine the wiring harness for damage or loose connections
Can I keep driving?
The car can still be driven, but starting may be difficult in cold weather.
General guidance, not a professional inspection. Confirm faults with measurements before buying parts, and use a qualified mechanic for brakes, steering, fuel leaks, airbags, and other safety-critical work. Terms and disclaimer