ML430 Check Engine On After Fueling
 

Can anybody instruct me on how I can fix the Check Engine light that came On. I did a fill up at Costco gas station and had the ignition key engaged so my wife can listen to CD music. The Check Engine never lit up before this, so I am assuming that was the problem. I know now I should remove the key (as a habit) before pumping filling up gas. However, can anyone give me a tip on how I can cure the problem since I heard they charge an arm and a leg to get it reset at the dealer. I was told maybe by unhooking the battery for some time can resolve the problem. Secondly, can a regular mechanic fix it? Thanks for any feedback. Johnny

or you can...
 

unplug battery for 20 seconds.. if it comes on again.. could be a air mass sensor =)) let us know how it goes...

to unplug the battery
 

do you just remove the clamp from the negative terminal, or is there a simpler way? Thanks

Gilly, don't chop my head off, I just want to understand the entire process, esp.in light of mpnye's response to tabo's comment about unplugging the battery. So, assuming the mass air sensor is replaced, would the check engine light go right out once the car is started, or does something have to be manually reset, or what? Please explain. Thanks.

I think u just forget to turn off the engine before fueling . The sensor just picked up that the pressure in the tank is on the loose , so it reports to the main comp and it sent u a warnning .

U dont need to take out the key .

nikorr

Re: ML430 Check Engine On After Fueling
 

One advice, NEVER disconnect the battery without properly shutting down the system on the MB.. Second advice, you don't need they key in the ignition to run the radio/CD. Just press on the ON/OFF button when you take the key out.

Now, you really don't have any problem. Here's what I [i]think happened[i]. The ML is LEV (ML500+) or ULEV (ML320). The emissions system is a closed loop system - i.e. the gas cap must be closed and there must be no leaks in the exhaust and fuel systems for proper functionality. With the ignition in (and I'm not completely sure whether you had the key in ACC or ON or just in the ignition) the system sensors are active and the open gas cap triggered them and you'll have the "Check Engine" warning - that's the way it's supposed to work!!!

I have to check my ML emissions sticker, but these vehicles may be in the class of vehicles that suck up refuelling vapors at the gas pump - ORVR (onboard refueling vapor recovery). If that's the case, the check engine light will come on.

In really don't think you have any problem. The system is working as it should.

Re: Re: ML430 Check Engine On After Fueling
 

Maybe it is just a fluke! If there is nothing wrong, the Check Engine light should reset itself after a few start ups.

Hey Gilly,

I think I just ran into the problem described in this thread. Do you agree the check engine light resets itself or should I visit the dealer. After three starts, it's still on!

Thx, Ed

You're in luck
 

I can get air mass sensors half price off Mercedes-Benz.. let me know if you want to save money.. my email is acura0@hotmail.com

Hi Ed
If your reasonably sure that the cap was left off, or if you refuelled with the engine running, I'd say give it more like a week.
Alot of it has to do with the length of trips you make and so forth.

If you don't think either of these things happened, then post another message with more info on the history of your problem.

Gilly

"NEVER disconnect the battery without properly shutting down the system on the MB"

I'm at a loss with this one. How exactly does one shut down a car's system? My battery died one day not too long ago. Does that count?

check engine
 

There was something about checking the cap, if it is not tight the light comes on.

Hi Gilly, After a few more starts the check engine light is off.

Yeah, I didn't tighten it properly so I think that was the only trigger.

Thanks again for your advice!

Ed