P0670: Glow plug module control: circuit fault
The ECU has found a fault in the circuit that commands the diesel glow plug module or relay, usually noticed as poor cold starting.
| Code | P0670 |
|---|---|
| System | Engine and transmission |
| Group | P06xx, Control unit and auxiliary outputs |
| Type | Generic: it means the same on every make |
| Can you keep driving? | With care |
What P0670 means
Diesel engines use glow plugs to heat the combustion chamber so the engine starts easily from cold. The ECU does not power them directly: it signals a module or relay, which sends them the current. This code means the ECU sees something wrong on that control circuit, such as a break, a short or a response that does not add up.
Most common causes
- Blown glow plug fuse
- Loose or corroded connector at the module or relay
- Damaged control wire between the ECU and the module
- One or more shorted glow plugs that have overloaded the module
- Faulty glow plug module or relay
- ECU fault (uncommon)
Symptoms
- Hard or slow starting from cold
- White smoke and diesel smell on start-up
- Rough running for the first few seconds
- Glow plug warning light (the coil symbol) flashing or not lighting
Can you drive with P0670?
With care Once warm the car drives normally, but on cold days it can be very hard to start or refuse to start. Best fixed before the weather turns cold.
Open the bonnetthe in-depth explanation
How to check it
With the engine cold, switch the ignition on and watch the coil-shaped light: it should come on for a few seconds and go out. A garage can check whether current reaches the glow plugs during preheating.
How to read and clear P0670 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0670 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P066C The cylinder 2 glow plug control gives a lower signal than normal
- P066D The cylinder 2 glow plug control gives a higher signal than normal
- P066E The cylinder 3 glow plug control gives a lower signal than normal
- P066F The cylinder 3 glow plug control gives a higher signal than normal
- P0671 Cylinder 1 glow plug: circuit fault
- P0672 Cylinder 2 glow plug: circuit fault
- P0673 Cylinder 3 glow plug: circuit fault
- P0674 Cylinder 4 glow plug: circuit fault
- P0600 Serial communication link fault
- P0601 Internal control module memory checksum error
- P0602 Control module programming error
- P0603 Internal control module keep alive memory (KAM) error
What does code P0670 mean?
Diesel engines use glow plugs to heat the combustion chamber so the engine starts easily from cold. The ECU does not power them directly: it signals a module or relay, which sends them the current. This code means the ECU sees something wrong on that control circuit, such as a break, a short or a response that does not add up.
Can you drive with P0670?
Once warm the car drives normally, but on cold days it can be very hard to start or refuse to start. Best fixed before the weather turns cold.
How do you clear P0670?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0670 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
