stumo
Senior Member
- Joined
- Sep 4, 2008
- Messages
- 431
- Reaction score
- 66
- Location
- VIC, Australia
- Your Mercedes
- ML270CDI x3 2002,03,04 | Sprinter 316CDI 2003 LWB
I'm just going to chime in here and say that I have had 2 MAF failures now on 2 different vehicles. On my vehicle ('02 ML270) the original MAF ran for several years without any issue after doing the EGR mod (Cat and Flap delete also done). Then the maf started putting the car into limp mode all of a sudden. Nothing else had changed on the car over these several years. So I put in a new maf sensor, and now the new sensor has only lasted 6 months.Yes, and I can not find any information saying otherwise. So I am going to keep on trying to figure this out!
2nd car this has happened on is a '01 ML270 (non facelift EGR mod but still has cats but no flaps). It had a new maf that only lasted 6 months too.
Both these mafs were genuine pierberg from the dealer.
So now the thinking is that the EGR mod circuit puts too much load on the maf sensor output driver. When you look at the circuit, when the EGR PWM gets pulled low, it basically loads up the MAF output circuit with an extra load in parallel to the ECUs high impedance input. So the output of the maf sensor goes from driving basically micro amps, to driving about 25mA through that 470ohm resistor and diode. I have no idea why my original maf lasted so long compared to the new one, but since I can only get new mafs now this looks like it is going to be a problem.
I think there might need to be some kind of isolation in the circuit to keep the maf output driver only driving a high impedance, like into a transistor or opto isolator. On the other side it can still have the pulldown resistor because the transistor/isolator will be driving that part of the circuit, not the fragile maf sensor output.
Thoughts?
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