P2678: The coolant expansion tank valve control circuit is open
The coolant expansion tank valve control circuit is open. A wire may be broken or a connector loose or dirty.
| Code | P2678 |
|---|---|
| System | Engine and transmission |
| Group | P26xx, Auxiliary outputs and cooling |
| Type | Generic: it means the same on every make |
How to read and clear P2678 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 P2678 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
- P2674 The injection pump fuel calibration needs its learning procedure
- P2675 The air cleaner intake control has a broken or disconnected wire
- P2676 The air cleaner intake control gives a lower signal than normal
- P2677 The air cleaner intake control gives a higher signal than normal
- P2679 The coolant expansion tank valve control circuit reads low
- P267A The rocker arm actuator position sensor circuit B (bank 2) is not working
- P267B The position sensor circuit for rocker arm actuator B on bank 2 is outside its
- P267C The position sensor circuit for rocker arm actuator B on bank 2 has a low signal
What does code P2678 mean?
The coolant expansion tank valve control circuit is open. A wire may be broken or a connector loose or dirty.
How do you clear P2678?
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, P2678 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.
