BMW E46 mass air flow sensor fault and testing

Symptoms are loss of power, jerking and turbo whine. The fault usually does not set a fault code until the sensor is almost dead, so the absence of codes does not rule it out. A loose or strained connector can cause the same symptom.

Unplug the sensor's wiring and drive. The engine control switches to a fallback map, and if the car then runs normally, the fault is in the sensor. If the car still stalls, the fault is elsewhere. The surest way is to try a known good sensor.

It depends on the car. On the M57 diesel, the new sensor (0928400468) must be coded if the car was built before 08/2001. On cars built after that, no coding is needed. Cleaning or removing the sensor does not require programming. Also make sure the arrow points in the direction of the airflow.