OBD-II code · Powertrain (generic, extended)
P2678 Coolant Degassing Valve Control Circuit / Open
The controller cannot drive the coolant degassing valve. Air pockets in the cooling system can form and cause local overheating.
Is it safe to drive with P2678?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyOpen coil in degassing valve
- PossibleBroken control wire
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.8–3 h
- Emissions test
- Usually unaffected
- Parts involved
- Coolant Degassing Valve, Solenoid, Wiring Harness
Related codes
- P2675Air Cleaner Inlet Control Circuit / Open
- P2676Air Cleaner Inlet Control Circuit Low
- P2677Air Cleaner Inlet Control Circuit High
- P2679Coolant Degassing Valve Control Circuit Low
- P267AB Rocker Arm Actuator Position Sensor Circuit Bank 2
- P267BB Rocker Arm Actuator Position Sensor Circuit Range/Performance Bank 2
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.