A.F.M air flow meter

[arrisbmw]

Hi I,m trying to understand how the electrical circuit works for the afm on our cars. IS it 4 wires to the unit .

12 v supply fused ?
earth
5v signal wire for the potentiometer adjusts with the flap
5v signal wire for the temperature sensor in afm.
is that right , simple diagram of just that circuit would be appreciated. and how it connects to the ecu.


thanks in advance.

[Brianmoooore]

It's three wires to the AFM - each end of the pot., and the wiper. Fourth wire is for the inlet air temp. sensor, which shares the same housing.
Circuit diagram here: http://www.autolib.diakom.ru/CAR/BMW/

[arrisbmw]

thats brilliant , thankyou vey much just what i wanted. can understand it better now.

am I wrong in thinking it,s got a fuse in the circuit ?

I assume the gry/yel wire is 5 volt signal from the ecu
and the gry/wht is the out put ref voltage that varies with with wiper position . and obviously the ecu uses that to determine flap position.


thanks again

[Brianmoooore]

You've got those the wrong way around.Grey/white is the constant voltage and grey/yellow is the varying voltage with flap position, the signal to the ECU.
No fuses anywhere.

[arrisbmw]

thanks again. I understand now.