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.
Affected components
- Aux thermostat a
- Engine coolant loop
Common causes
- High likelihood: Thermostat element failed
- Medium likelihood: Wax pellet aged - element non-responsive
- Low likelihood: Carbon or debris buildup preventing free movement
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Related codes
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.