Coolant temperature sensor
Check that coolant and charge air are approximately the same temperature when the engine is cold.Check the coolant temperature sensor, charge air pressure sensor, charge air temperature sensor, fuel supply pressure sensor and fan speed sensor, along with the connectors and electrical cables in the circuit.Proceed as follows to verify that the fault has been rectified:Switch the power off and on with the starter key.If the fault has been rectified, the fault code becomes inactive. Clear the fault code.Switch the power off and on with the starter key three times in succession at 10 second intervals to extinguish the warning lamp.
What you'll see
No driver-visible symptom recorded.
System reaction
There is a common power supply for the coolant temperature sensor, charge air pressure sensor, charge air temperature sensor, fuel supply pressure sensor and fan speed sensor. If a fault occurs in one of the sensors, this can affect the circuits of the other sensors.If the voltage is outside the permitted range, the control unit uses a preprogrammed value. If the engine is actually colder than the pre-programmed value indicates, the engine will run more roughly when idling and will be more difficult to start.The engine will run at fixed raised idling speed as long as the fault is active.On engines with EGR, the engine control unit will switch off the EGR system.The fault affects the vehicle's emissions of nitrogen oxides (NOx) and the lamp which warns about a high level of contaminants comes on in the instrument cluster. A text message is also displayed on vehicles with NOx control.Vehicles with NOx control An active fault code cannot be deleted from the control unit. When the fault has been rectified, the control unit must verify that the fault has been rectified in order for the fault code to become inactive.
Diagnostic depth
The voltage in the circuit has been above the permitted level.
Possible causes:- Open circuit in coolant temperature sensor circuit. - Fault in the circuit of the coolant temperature sensor, charge air temperature sensor, fuel supply pressure sensor or fan speed sensor.