Mercedes Benz – Check Engine Light On and Vehicle Won’t Move

Reader Question :

Dear sir,

I would like your honest opinion as in the past your suggestions turned valuable to repair my old Chevy. Yesterday I bought 2001 Mercedes-Benz ML320 and as soon as I drove it on the road I got the Yellow Engine Check light ON. Once it did that I could not accelerate the car faster because the rpm would not switch the gear Even though my gear was on D – Drive.

I took the car for the electronic diagnosis and the technician told me that he stored the transmission code but he said your car showed some thing know as Sporadically Rpm sensor n3y3/611 is faulty and advised me to replace them at a mechanic place.  The rmp sensor goes into a loop.

After this check the Engine Check Light does not show any more. I think the technician did update or reset the computer which is why the Engine check light is not coming up again. My question is shall I drive it until the Engine light comes ON again or Shall I take it to repair center and replace the rpm sensor.

The dealer who I bought this car from yesterday told me to just drive it until I get the check engine light comes ON again.

Regards, Habib

Hello there Habib,

My honest opinion would be to take this vehicle back and get a refund immediately.  I would never keep a vehicle that showed signs of trouble on the way home after the sale.

A 9 year old Mercedes……you are just asking to spend lots of money on regular maintenance let alone un-forseen problems like this.

How many 9-10 year old Mercedes do you see on the road on a daily basis vs 1-3 year old Mercedes?

Mercedes is a great vehicle, but once they start to show problems you are better off getting rid of them than dumping tons of cash into them.  I would suspect this vehicle was sold because of this strange problem no one would figure out.

You are going to need to see a Mercedes mechanic who knows these cars inside and out, I am not one of those mechanics.

It does sound like a problem with the VSS (vehicle speed sensor) but that is just a wild guess.

I would NOT guess with this, the parts are too expensive. So spend the extra money and go to the dealer or find a Mercedes specific repair shop.

Maybe, if the dealership wont take the vehicle back for a full refund, they will pay the repair bill.

You can probably get your money back via the lemon law since you had an issue immediately after the sale.

I would much rather see you get out of this vehicle and into a Lexus, which is a much more reliable and economically viable maintenance wise.

Sorry to have burst your bubble. 🙁

Austin Davis

Posted in: Lemon Law Issues

2 Comments on "Mercedes Benz – Check Engine Light On and Vehicle Won’t Move"

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  1. Ken says:

    Lexus? Random acceleration problems are better than check engine lights? It’s true that the Mercedes will cost more to own but well worth it. These vehicles are amazing. You have to be wary that the vehicle may have been in an accident, previously. Do a carfax on it. If it was, then I would demand a refund. I agree that, I would request that, the seller perform the repair or pay for the repair. I was a certified Mercedes Benz technician for 7 years. Definitely take to a Mercedes Benz certified repair facility. Sometimes it just requires calibration or coding in the control unit changed. Not always but sometimes.

  2. Gusty says:

    Not to argue with the boss here, but here’s something you could check:
    My Merc, (W211 E240 2002) was displaying ESP DEFECTIVE – TAKE TO WORKSHOP, at what seemed to be totally random intervals, and also, like you, literally while driving out of the driveway of the previous owner. The previous owner told me to switch it off and on, and that got rid of the problem, which recurred at ever-increasing intervals. I ‘updated’ my old (W124 E200 1991) Merc to have a more reliable car, so as you can imagine, this caused me some grief. The official Merc repair center could not discover a problem, but a private car electrician found the problem in fifteen minutes: the satellite tracking alarm was installed after purchase, and someone wasn’t paying attention, and clipped the elbow rest onto the alarm cables, as well as re-attaching the front under-dashboard panel onto the footwell lighting. As you can imagine, the clips cut the wire, shorting immediately, and the light bulb melted the other wire’s insulation, shorting it also… over the course of time, and constant heat due to the short, the immobiliser wire shorted across the control cable ribbon coming out of the front computer panel (W211 has 3 computer panels, front, middle and back), I guess sending random signals to everywhere. On inspection, one leg of one chip was burned to dust (!) on the front computer panel.
    My costs (and please bear in mind I am in eastern Europe!) for the following repairs was about 3 weeks of waiting and 250 USD equivalent:
    Front computer panel obtained from junkyard
    The removal and replacement of all interior paneling to check for shorts that may not have been visible
    Replace all shorted wiring.
    The car now exhibits no signs of former trouble, in fact overall electronic ‘ghosts’ (I call this the Christmas tree effect – when colourful random lights appear all over the place) has ceased.
    Repeat, NOTHING to do with ESP, or the age of the car, one cack-handed alarm technician was enough. I have no doubt the previous owner wanted rid of the car for this reason.
    Along the way, there was a computer reset, that resolved the problem for a few months.
    I would CERTAINLY agree with the boss here, don’t drive the car until you are sure what was wrong with it, and that it’s fixed.
    The only signs of age related problems are that the BAS (break assist servo) is ‘grumbling’, which I understand from various mechs to be completely normal after eight years, and this will need to be replaced at some stage.
    So if you are a patient and dedicated merc fan, it’s worth asking your mech to go digging in the computer wells in the car – this is how my problem was discovered. I can’t advise you on the cost/benefit, that’s something you’ll have to work out for yourself, because your costs are unlikely to be as low as mine were. Again, in total agreement with the boss, if you can get your money back, that may well be the quickest way of solving this problem. If you can’t, it’ll be an adventure for sure.
    Further symptoms:
    Needing to wait after inserting the ignition key, before turning. – Resolved.
    Airmatic suspension is not pumped up. – Resolved.
    Message: “ELECTRICAL CONSUMERS NOT TURNED ON”, car otherwise fine. – Resolved.
    Low battery after 4-5 days of standing, probably leading to above error message. – Resolved.
    Good luck!

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