P026F
Coolant Thermostat Performance
Thermostat does not regulate coolant temperature in the expected range. Often stuck open (slow warmup) or stuck closed (overheat).
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Thermostat stuckCommon
Parts involved
- Thermostat
P026F 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.