P26BB
Engine Coolant Bypass Valve C Range/Performance
The third coolant bypass valve responds to commands but the resulting coolant temperature behaviour is not as expected.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Valve partially stuck by sedimentCommon
- Weak return spring fails to close fullyPossible
- Sensor element aged beyond calibration windowLess likely
Parts involved
- Coolant Bypass Valve C
- Thermostat Housing
P26BB 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.