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.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Open coil in degassing valveCommon
- Broken control wirePossible
Parts involved
- Coolant Degassing Valve
- Solenoid
- Wiring Harness
P2678 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.