P0670 Glow plug control module circuit/open
What P0670 means
The engine control unit cannot properly command or monitor the glow plug control module on a diesel engine. Without it the glow plugs may not heat, making cold starts difficult.
P0670 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Medium
- Typical repair cost
- 120–450 €
- Workshop time
- 0.5–2.5 h
- Repair difficulty
- Medium
- DIY possible
- No
- Check engine light
- Yes
- Affects emissions test
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Hard starting in cold weather
- White smoke after a cold start
- Glow plug light on or flashing
- Check engine light on
Common causes
- Faulty glow plug control module or relay
- Broken or corroded wire between the ECU and the module
- Blown glow plug system fuse
- Shorted glow plug overloading the module
Can I keep driving with P0670?
You can keep driving, but have it fixed within one to two weeks, especially before cold weather.
What to check first
- Check the glow plug fuse and the module connector
- Check the control signal from the ECU to the module
- Test each glow plug for a short circuit
- Replace the glow plug control module if inputs are correct but it does not switch
Related codes
- P0660 Intake manifold tuning valve control circuit/open (bank 1)
- P0650 Malfunction indicator lamp (MIL) control circuit
- P0645 A/C clutch relay control circuit
- P0628 Fuel pump A control circuit low
- P0627 Fuel pump control circuit/open
- P0620 Generator (alternator) control circuit
- P0615 Starter relay circuit
- P0610 Control module vehicle options error
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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