P2CF0Auxiliary Thermostat A Stuck Closed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2CF0 is the closed-side counterpart of P2CEF: auxiliary thermostat A fails to open, so the circuit it governs gets too little flow and its temperature climbs past the regulating point while other parts of the engine may look normal. No manufacturer documents P2CF0 publicly. The same component is described by Lotus for the four-cylinder Emira, where A is the medium-temperature thermostat and the workshop test checks that the cold piston is retracted and extends in hot water; a unit that never extends would match this code. Wax thermostats usually stick shut when the wax charge leaks or dirt jams the piston. CARB has required monitoring plans since 2019–2021 for systems with several thermostats and temperature sensors. Overheating in that loop is the risk, so it needs prompt attention.
- What you may notice
- Engine warning lamp
- High temperature in one cooling circuit or an overheating warning
- Possible power reduction to protect the engine
- Likely causes
- LikelyWax element lost its charge, thermostat no longer opens
- PossiblePiston jammed by deposits or debris
- RareAir pocket around the element after a coolant service, so it never sees hot coolant
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €150 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.