P0172 Engine Code after MAF change

[abtekk]

Hi guys,

The other day I changed the MAF sensor on my C200 W203 to fix the engine light that was caused by it, but the day after I started having issues with acceleration, idling, etc and the Engine Management light came back on with P0172. What are the steps to diagnose the issue? I still have the old sensor somewhere, but I'm wondering if it's something I've done when changing the sensor.

All help appreciated.

Abtekk

EDIT: looking at other places, I need to do a "drive cycle" after disconnecting the battery so that the ECU can learn the values for the new sensor. I can only find instructions to do that in an automatic, though. My car is a manual transmission.

 

[ashenfie]

No idea about drive cycle as there is noting for the ECU to learn, that may relate to the Auto gearbox.

Things is could be are;

• A dirty/wrong mass air flow sensor overstating the amount of air entering the engine which may cause excessive fuel delivery
• A bad oxygen sensor
• A leaking fuel injector allowing too much fuel to enter the combustion chamber
• A faulty fuel regulator, which may not be regulating the pressure of the going to the engine as it should
• A vacuum leak
• A possible fault in the coolant system such as a stuck thermostat or bad coolant temperature sensor

I would be temped to revert to the old MAF and see what happens, you may just have the wrong one for your car.

 

[abtekk]

No idea about drive cycle as there is noting for the ECU to learn, that may relate to the Auto gearbox.

Things is could be are;

• A dirty/wrong mass air flow sensor overstating the amount of air entering the engine which may cause excessive fuel delivery
• A bad oxygen sensor
• A leaking fuel injector allowing too much fuel to enter the combustion chamber
• A faulty fuel regulator, which may not be regulating the pressure of the going to the engine as it should
• A vacuum leak
• A possible fault in the coolant system such as a stuck thermostat or bad coolant temperature sensor

I would be temped to revert to the old MAF and see what happens, you may just have the wrong one for your car.

Hi, thanks for this.

I popped in the old MAF and the car runs fine, so that must mean it's the MAF, not the other points you mentioned, right? If I pay attention I can counteract the effects of the new MAF, and I'm still getting about 26MPG in regular traffic. Could taking it for a good run down the motorway help?

 

[abtekk]

Just bumping this as I could do with a second opinion if the new MAF is faulty before I replace it.