Mercedes-Benz W212 CDI: fault code P0101 and mass air flow sensor
W212 CDI: what can cause fault code P0101?
The code does not always mean a faulty mass air flow sensor (MAF). The cause can be a crack in the charge air pipe (e.g. on the underside of the pipe after the intercooler, not visible from outside), a deviation in the boost pressure sensor, or an intake manifold pressure sensor that differs too much from the other pressure sensors. The sensor readings are compared with the engine off.
P0101 comes on in a W212 after an air filter change, what should I do?
The filter change must be registered in the system with the Mercedes diagnostic tool (STAR), and the mass air flow sensor test or adaptation is run. If the reset has not been done, the fault can remain even though the parts are fine. Have a workshop do the reset.
What is the normal air mass at idle for the OM651 engine?
On the OM651 the air mass at idle is about 300 mg/Hub. Over 500 mg/Hub is too high and points to, for example, a leak or a blocked air filter. The reading is viewed on the diagnostic tool.