P0126 - Insufficient Coolant Temperature for Stable Operation
Engine Coolant Temperature is monitored to allow the ECM to accurately adjust fueling and emission control systems, it will also normally be used to control cooling fan operation.
Fault Code Explained
The ECM has detected that the Engine Coolant Temperature as indicated by the ECT sensor has not reached sufficient temperature for normal engine operation quickly enough after engine start.
If possible use a diagnostic computer to view live data for the ECT sensor and compare to actual engine coolant temperature.
If the Actual Coolant Temperature matches the sensor value and the engine is running colder than normal it is recommended to carry out cooling system checks to establish reason for cold running
- Check operation of thermostat
- Check cooling fan not running constantly
If the actual engine coolant temperature does not match the sensor value it is recommended to check the sensor and sensor wiring