Good and faulty MAF

VW uses several Bosch MAFs for its TDIs. Bosch number 0 281 002 216, VW number 028 906 461 and also Bosch number 0 280 217 121, VW number 06A 906 461. These MAFs are equal, except for the length of the housing.

Faulty Bosch Mass Air Flow sensor

The graph below was measured on a 81kW TDI (engine AFN, after 180,000 km) under WOT (wide open throttle). As can be seen clearly, the specified air flow is much higher than the actual (measured) air flow. Turbo pressure reached 2000mbar, so turbo seems to be fine. Also the intake manifold was not fouled by soot and oil.

The circle in the graph shows the 3000RPM WOT point. Here you should read 850mg/stroke MAF (specified and actual). Turbo pressure should be 2000mbar. (not in this graph)

Reading the fault memory of the ECU did not show any errors. Still the owner felt his car was lacking response to the go pedal.

Good Bosch Mass Air Flow sensor

A new MAF on the same engine immediately cured the problem. Power returned, specified MAF and actual MAF are equal again.

The 3000 RPM WOT point shows 850mg/stroke. As can be seen, actual and specified MAF are not always exactly the same. This is normal.

In the graph below another reading with an AHF engine (same MAF as in AFN) is shown. Full throttle acceleration from first till fourth gear (manual shift). Shift points at 47, 53 and 60 seconds. Specified MAF is 850mg/stroke at 3000 RPM. The actual MAF is also 850mg/stroke: The MAF is okay.

Page Last updated: 11/14/2002