ML270 auto box problem

[steve1964.138]

Hi, I'm Steve, a newbie on this forum, & new to Mercs.
I recently bought a '02 ML270 with 107k miles, full history (not MB for a while) to tow my mobile chicane (caravan).
It has been great to drive (I had a V6 Grand Vitara before!) but has just started playing up. I'm sure this has been covered before but i've spent a few hours looking & can't find an answer so here goes.
Every now & again the box seems to slip, the revs pick up but acceleration is slow. It did it coming off a roundabout onto a dual carridgeway where it got up to 60mph but wouldn't change up a gear, it was doing (i think) 3000 rpm. I've tried changing gear manually but nothing happens, it stays the same. I have to stop the car, turn off ignition then re-start & alls good for a while. On a 200 mile round trip last weekend, 160 miles on dual carridgeway, the rest starting & stopping, it did it 4 times.
A mechanic friend put it on his fault finder & it came up with the following, all stored
P2203 The internal electrical check of component Y3/6n3 (speed sensor 3) has failed
P2502 The gear is implausible or the transmission is slipping
P220A The speed comparison of Y3/6n2 to Y3/6n2 is implausible.


He suggested I look up the codes on the net as he didn't know what that all meant, but it seems to agree with my experience.
I followed a link on this forum and fiound the first one says NOx sensor circuit high imput, the second one says charging system voltage & the third came up as not recognised.

Anyone have any idea what it may be?
I wait in hope & anticipation for several different answers (i'm a regular on another forum

).

BTW, one reason I was looking for so long was that i kept getting sidetracked reading some excellent threads

 

[Mickybo]

Welcome to the Forum, going to start with the first obvious question, have you checked the ATF level?

 

[jerry270ML]

I dont know if the codes are related with your gear box problem . Usually this kind of problems are solved changing the oil ,filters and electric plate of your gear box . I had/have this problems with my ML270 and I don't even use it to tow a caravan or anything else.
722.6 gearbox gives a lot of headaches !!
Sorry to disappoint you .

 

[tonyc280]

I dont know if the codes are related with your gear box problem . Usually this kind of problems are solved changing the oil ,filters and electric plate of your gear box . I had/have this problems with my ML270 and I don't even use it to tow a caravan or anything else.
722.6 gearbox gives a lot of headaches !!
Sorry to disappoint you .

What is the electric plate in the gearbox for as i have a 722.6 box myself. Cheers tony.

 

[steve1964.138]

Thanks for the quick replies guys.
Mickybo, no, I haven't checked that yet, I'll do it today if i can. I was going to get it changed anyway as there's no record of it being done.
Jerry270ML, I'm hoping it is realted, the codes mention slipping.

As i've only recently bought it I haven't towed my caravan yet, that is due to happen this weekend .......possibly!

 

[Mickybo]

It is meant to be done every 40k, not a difficult job, I done mine on my driveway in about an hour, new filter, gasket and ATF

 

[Terry_]

I would say a fluid and filter change to start. The speed sensor fault unfortunately does not usually relate to fluid.
A new conductor board will be required to cure this I would imagine

 

[steve1964.138]

Well, it's booked in here MBS Family-run Mercedes & BMW service and repair specialists in Exeter, Devon on monday.
I'll report back with their verdict

 

[jerry270ML]

Well, it's booked in here MBS Family-run Mercedes & BMW service and repair specialists in Exeter, Devon on monday.
I'll report back with their verdict

What they said ?

 

[steve1964.138]

Sorry it’s been a while, some other stuff had to take priority.
MBS told me there were a few things wrong with the car, most only minor things but tellingly the speed sensor in the gearbox was faulty & the battery was the wrong one for the car.
They gave me a price of £400-£500 to fix the gearbox.
Just after this the alternator packed up so I had it sorted & bought a new battery. I was told it was possible the battery could have been affecting the sensor so it seemed worth trying it first.
No such luck.
I called another garage who agreed the sensor could be the problem but it could be a worn gearbox! They said the price was about right, the plate was £200 then there was oil, filter & seal. Labour & VAT completed the price.
2 questions. He said plate, not sensor. Are they the same thing?
Having read through several posts on this forum & followed links, I’m confident I could do the work myself. I just need to know which parts I would need.
Question 2, where can I get these parts at a sensible price?
I’m still driving the car, the ‘slipping’ only happens occasionally, normally after more than 20 miles or so, sometimes it’s fine for longer. It passed it’s MOT last week so I only really need to get the box sorted now to have an excellent car.

 

[Bobby Dazzler]

I would also add the MAF (or air mass meter) to you list of likely suspects. Ours failed whilst towing and the symptoms were eerily similar to yours, and cost £55 and 10 minutes to fix, so might be a good one to eliminate before you spend money on big repairs - replacing the MAF should be on the service schedule!

Search the forum for MAF - here's one thread I found: http://www.mbclub.co.uk/forums/engine/118410-ml-270cdi-limping-max-3000rpm.html#post1310059

 

[Vlad]

I would also consider the MAF...quite common at this mileage. Do ensure that you buy one from MB rather than aftermarket. Not that expensive from MB which is a surprise.

 

[BlackC55]

If its slipping then I would suspect a worn gearbox if the atf level is ok. There is a code for the speed sensor so I suspect that is faulty too.

 

[BlackC55]

If there is no fault code for the mF I would say it is probably ok.