Outdoor temperature sensor (T27) or temperature sensor upstream compressor (T126)
Start the engine and drive the vehicle at a speed above 40 km/h for approximately 10 minutes. Check the Outdoor temperature sensor (T27) and the temperature sensor upstream of the turbocharger compressor (T126), to see which temperature is reasonable. A check can also be made with an external thermometer ( placed as close as possible to the sensor ). Fault trace the suspected temperature sensor ( wiring and connectors ) Replace sensor if no other fault is found. Verify that the problem is solved by switching off the power with the starter key and waiting for 15 seconds. Start the engine and drive the vehicle at a speed above 40 km/h for approximately 10 minutes.
What you'll see
No driver-visible symptom recorded.
System reaction
The check compares the temperatures from the Outdoor temperature sensor (T27) and the temperature upstream of the turbocharger compressor when the vehicle is driven. The check can be carried out more rapidly if the vehicle is driven at high speed. The EGR/SCR system is switched off when the measured outdoor temperature is too low. In accordance with current legal requirements, the engine power is reduced on vehicles which have NOx control. EuV: The fault code cannot be cleared when it is active.
Diagnostic depth
The Outdoor temperature sensor (T27) displays too high a value, or the temperature sensor upstream turbocharger compressor (T126) displays too low a value.
Possible causes: - the Outdoor temperature sensor (T27) or the temperature sensor upstream of turbocharger compressor (T126) are defective - Manipulated Outdoor temperature sensor (T27)