Thermostat Heater Control Circuit Open
The map-controlled thermostat - electrically heated to lower its opening temperature on demand for emissions or torque mapping - has an open control circuit. The ECU loses the ability to override coolant flow timing.
Affected components
- Map thermostat heater
Common causes
- High likelihood: Open in heater element or harness
- Low likelihood: Pin pushed back out of connector body
- Low likelihood: Cracked solder joint inside the module or sensor
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
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.