OBD-II code · Powertrain (generic, extended)
P2CF2 Auxiliary Thermostat B Stuck Closed
The auxiliary thermostat B is stuck closed. Coolant cannot flow through the affected branch, risking overheating in the bypassed path.
Is it safe to drive with P2CF2?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyThermostat element failed
- PossibleWax pellet aged - element non-responsive
- Less likelyCarbon or debris buildup preventing free movement
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–3 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Aux Thermostat B, Engine Coolant Loop
Related codes
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.