Hi,

I have a 2005 limited manual coupe (Australian delivery if that makes a difference) with 40,000 klms. It has been back to the dealer twice now for a engine warning light that comes on and off. Lately its getting worse. It will come on and stays on from about 3 days then may go off for a day, then back on even on the same tank of gas. I only ever use the premium petrol 98 octane. The dealer replaces the sensor then its ok for about a day then comes back on. One time he fixed it, drove it to the front and it came on again?

Any ideas???

Thanks in advance.

 

not without what OBD2 code you are getting and what sensor they are replacing ... as well as more info on environment the car is driven in, but the second is useless without the first.

 

Engine warning light - do you mean the Check Engine light? If so then make sure your gas cap is on tight. If the cap is loose it can cause the Check Engine light to come on.

 

I had a similar problem with an ML320 Benz. A sensor that is intermittently bad will throw the check engine light and then after you start the engine about three time the light will clear only to come on again the next time the sensor fails. Did they tell you what codes are being thrown? Or what sensor they changed? Some codes can relate to multiple problems/sensors which can make changing the right sensor more of a challenge. you might need to find a mechanic more experienced with these engines or take it to a Mercedes dealer or private mercedes mechanic. Probably not an option as you want this covered under warrenty?

 

I agree...without knowing what trouble codes are passed, there's too many options.

Without narrowing it down you have to resort to the "grocery cart" method! Buy 1 of everything and start replacing parts till it's fixed.

 

Thanks everyone for your comments. I will make sure I ask what the codes are next time. The one thing he did say last time was the code was listing a fault related to some sensor in the tank, upon investigation he also said the Australian version doesn't have a sensor in the tank so I dont know what's going on there!

Going forward - it was suppose to go in this morning as the light has been on last three days, on the way to the dealer it decided to turn off again (typical!) so the dealer has ask me to wait and bring it in straight away next time. If I find out anymore I will list details.

Thanks again,
Adam

 

I have lots of ideas, but you should just run a scan on the pending and active DTC's and then none of us will be guessing and you won't be wondering...