Fault-Code Library · Diesel preheating
P0670: Glow-plug control module circuit
The engine controller detects a fault in the glow-plug module or its main control circuit.
Common symptoms
- •Hard cold starting
- •White smoke after start
- •Uneven cold idle
- •Glow-plug warning
Likely causes
- •Failed glow-plug module
- •Power supply or fuse fault
- •Harness damage
- •Multiple failed glow plugs
First checks
- •Check module power and grounds
- •Scan individual glow-plug faults
- •Measure plug current or resistance correctly
Important
Glow plugs can seize in the cylinder head; use the correct removal procedure rather than excessive force.
A fault code identifies a detected condition, not a failed part. Confirm manufacturer-specific subcodes and live data.
Related research
Continue your research
Move from brand context to exact model, powertrain, fault-code, and buying-checklist evidence.
Buyer help
Request a used-car risk review
Send us the model, year, engine and mileage. We'll help identify the main risks before you buy.
Known engine and gearbox weak points.
Fault codes and symptoms to verify.
Inspection questions before negotiation.
This is buyer guidance, not a remote mechanical inspection or a guarantee. Always verify the car in person with diagnostics and service records.