insame1

I posted this in the amg section but got no response. I m hoping some here may have some insight
My car is throwing a p0446. I took it in to an indy who suggested I replace the evap switch under the hood, gas cap and valve cover gaskets. I did all that and got the code again. I took it to MB of Austin and they said it was the charcoal canister, shut off valve and MAF I replaced all of those too and still get the code. They were all replaced with oe mb parts. What is there left to do? Oh. I replaced the harness at the shut off valve also

Rudeney

Your indy wasted your time and money. MB of Austin was correct, except for the MAF sensor is unrelated. It is a problem usually related to the shut-off valve on the charcoal canister (right side rear wheel well). When replacing that does not fix the problem, the next step is to check fuel tank pressure for leaks. If it is good, then the pressure sensor needs to be replaced.

insame1

I agree the only reason I did waht the suggested is I was out of options at the time. I replaced the canister, valve, and harness. One thing the indy suggested that I didnt do is the fuel tank presure sensor as I replaced the sending unit less than a year ago. I fear now that I messed up wiring the new plug for the sending unit / sensor. Thanks as always.

insame1

I took the car to another dealer. They had the car for 5 days and said it was a faulty pressure sensor. Swapped that again and got the p0446 code again. I'm lost.


rudeney.... I'll get the part number off the sensor tomorrow. They had it at the dealer in Georgetown tx.

Rudeney

Did the dealer do a pressure test, or just replace the sensor?

insame1

no pressure test. They said it was reading -43. I think I wired it wrong. I just don't know what wires do what. I'm going to have to test for 12v and swap the other 2 I guess. That's about all I have to go on right now. Im thinking about buying the Mb conversion harness and going to a wrecker to get an original oe connector.

I'm not very confident in there methods thought. A. They said canister and shut off valve first even though they knew it had been replaced. B. When they suggested the sensor they said they were going to have to drop the tank. On the plus side they only charged me for 115 for the sensor and no labor.

Rudeney

On some models, the pressure sensor does require dropping the tank, but on the W209, it's on the sender unit, accessible under the seat. I was not aware that the pressure sensor could be replaced by itself. I thought the entire sender had to be replaced.

insame1

I don't think you can replace the sensor on the original unit. On the new ones the part number is 12223069. There are a bunch of cars that use this part and I belive it is manufactured by gm.