[cnpnh11]

Hey Everyone,

The other day, for the first time since I've owned the car, the check engine light came on. Having previously owned BMWs, it was nice to see how discreetly MB chose to place the location of the light (where the clock is at about 3). The BMW (5,3s) that I drove had it big and bold right at the bottom of the cluster! Anyway, I took the car down to AutoZone to have them pull the code for free since my local MB Dealership costs $125 to do the same thing. The codes that came up were all related to the fuel/vapor sensors in the car. I've tried to poke around for info online and most forums say that if this is the case, to tighten the gas cap and the light will probably shut off in a day or two if this was the only problem.
I'm wondering if there is any way to verify if this was the problem? Is there a way to shut the light off and see if it comes back on? Has anyone else had a odor of gas in the cabin before? I have an odor when I fill the tank (usually not too bad) and I had the MB dealership checks the seals, etc. and they said they're all fine. I'm just wondering if this could be related somehow. Any thoughts from anyone else out there on this issue? I've caught the MB dealership bs'ing me in the past, so I really don't want to have to rely on their input. Thanks!

 

[lkchris]

Not so sure "tighten the gas cap" is the solution.

More like replace it because the seal is bad. More tightening doesn't really fix a bad seal.

If the problem is fixed the light will go out. This is kind of the inverse of turn it off to see if it's fixed, but it's really the same thing.

 

[cnpnh11]

Do you think replacing the gas tank cap could possibly be the solution? Is this the type of thing that would trip the Check Engine light? I was wondering if it was related to the gas smell that sometimes fills the cabin. However, the odor issue has been there on and off for a few years, but this is the first time the light has ever come on so I doubted it would be the culprit. Doy you have any troubleshooting tips (hopefully in order from cheapest to most expensive) that I could take a shot at to figure out the light?

 

[paulv]

Codes, please?

You mentioned that AZ read the codes for you -- what were they? These cars typically have P0440, 42, 43, 46, 50, 55, and 56 that are related to the EVAP system and will all trigger the CEL. As mentioned before, when the problem is fixed, the CEL will go out (usually after 1 cycle, and the CEL will come on after 1 or 2 drive cycles, depending on the code).

If all the EVAP components are operating OK, then the system needs to be smoked to find the leak.

Regards,
paul...