Powertrain
generic / SAE
P2CEF
Auxiliary Thermostat A Stuck Open
The auxiliary thermostat A is stuck open. Coolant flow bypasses the thermal regulation, leading to slow warm-up and reduced engine efficiency.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / numberC / EF
Possible causes
- Thermostat element failed high
- Wax pellet aged - element non-responsive medium
- Carbon or debris buildup preventing free movement low
Inspection / repair
- Difficulty: medium
- DIY: possible
- Estimated cost: 60–400 €
- Estimated time: 0.5–3 h
- Component: aux thermostat a
- Component: engine coolant loop
- MIL / check engine light
- emissions-relevant
- drive cycle required
Sources
References
sae:J2012