P26AF
Engine Coolant Bypass Valve B Stuck/Open
The second coolant bypass valve is stuck in the open position. Coolant always bypasses the second radiator path.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Valve seized open by sedimentCommon
- Broken return springPossible
Parts involved
- Coolant Bypass Valve B
- Thermostat Housing
P26AF 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.