Mass flow sensor
Check the mass flow sensor, oil pressure sensor and fuel temperature sensor, along with the connectors and electrical cables in the circuit.Proceed as follows to verify that the fault has been rectified: There must not be any active fault codes for the voltage supply to sensors or for battery voltage. Start the engine and run it at idling speed for at least 15 seconds. 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 mass flow sensor, oil pressure sensor and fuel temperature sensor. If a fault occurs in one of the sensors, this can affect the circuits of the other sensors.The engine runs with EGR but without any feedback from the mass flow sensor. The control unit will therefore only roughly control the EGR content using the predefined values on the EGR damper position. Calibration of the mass flow sensor is switched off.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 controlAn active fault code limits the maximum engine torque by approximately 40% after the engine has been running for 50 hours.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 are:- Open circuit in mass flow sensor circuit.- Fault in the fuel temperature sensor circuit or oil pressure sensor circuit