Old Merc in limp mode after new cat fitted.

[Finn66]

Hi all, just looking for a few expert opinions. My 1999 CLK 2.3k convertible has just passed it's MOT after having a new catalytic convertor and O2 sensor fitted. However, when I drove the car home, the gearbox thumped into gear and then stayed in one gear which I'm told is 'limp' mode. I took the car back to the garage who checked it over but could find no obvious cause. They couldn't read any diagnostic codes due to the age of the car and suggested a local MB expert (who I have used before) but he is still on his Xmas hols. What I am wondering is whether there are any plugs or linkages that might have been dislodged or damaged by the fitting of the new cat or whether it is just an unfortunate coincidence.
Thanks in advance.

[Cylon2007]

All cars since 1996 should have OBDC fitted so there should be a way to read any error codes. Also if it ran fine before the garage did fitted the CAT it makes sense that something they did has caused the issue. I would be expecting them to sort it out.

[Finn66]

Hi, thanks for the response. My CLK has the 38 pin Mercedes Star diagnostics port under the bonnet rather than the standard OBD port hence the suggestion that I have it checked by the local indie who has the relevant equipment. I'm just going to have to wait for him to return to work and read the codes. If the findings suggest the garage are to blame, I will return the car to them.
Once again, thanks for taking the time to reply.

[stevieturbo]

It is very possible the problem may have been caused by the work, or it may be coincidence. But certainly removing exhaust etc, they may well have disturbed some wiring.

And pretty sure that car should have a regular DL16 socket for OBD even if they call their own software something different. Any decent gear should be able to get info from engine and gearbox ecu's

If it's a cheap phone app you're using, then no it will be of limited use.

[Old Merc]

The garage who did the job is responsible, it may just need the ECU resetting? Trouble is the only guys who can do it is a Mercedes Specialist.
The genuine Merc` kit is far more sophisticated than any of the diag tools local garages have.
You should inform your garage that the car is going to the Merc` man and you want them to pay the bill.

[Elliot2000]

Old Merc said:

The garage who did the job is responsible, it may just need the ECU resetting? Trouble is the only guys who can do it is a Mercedes Specialist.
The genuine Merc` kit is far more sophisticated than any of the diag tools local garages have.
You should inform your garage that the car is going to the Merc` man and you want them to pay the bill.

It’s an old car, there is every chance that something has failed with no link to the work done. Obviously, there is a good chance that it was something that’s been done by them, but it’s not guaranteed. It sounds like the OP is going on with the right idea - get an expert to look at it and see if it related to what they have done rather than going in blaming them straight away.

[GreenV8S]

Old Merc said:

You should inform your garage that the car is going to the Merc` man and you want them to pay the bill.

Maybe that works for you, but I don't believe any of the garages I've worked with would agree to that.

If you believe your garage caused the problem then you need to send it back to them to fix. They might end up sending it out to a dealer, but that's their choice. Bear in mind it's possible this is unrelated to the work they did and in that case you'll foot the bill for the new problem.

[stevieturbo]

Old Merc said:

The garage who did the job is responsible, it may just need the ECU resetting? Trouble is the only guys who can do it is a Mercedes Specialist.
The genuine Merc` kit is far more sophisticated than any of the diag tools local garages have.
You should inform your garage that the car is going to the Merc` man and you want them to pay the bill.

How do you know they are responsible ? Are you privvy to some other facts here ?

And any decent diagnostic gear you'd expect any garage to have would be able to communicate with all the modules necessary. Any competent garage doesnt use a £10 plug/adapter and phone app you know.

[Finn66]

Thanks for your input, guys. As I mentioned earlier, the car uses a pre-standardized diagnostic system which the garage can't access. There is an outline of an OBD port under the dash which was obviously put there in readiness of Mercedes Europe catching up with our American cousins who implemented the standard format from 1996. I have previously had an AA patrol man connect his diagnostic computer to the car by way of an OBD 16 pin to 38 pin adapter but he could only access basic information. The MB guy's system goes much more in depth. Hopefully, I will only have to wait a couple of days to get the codes read and even more hopefully, they will point to something quite simple. I will update when I know.
Ps- The garage that had the car have looked after it for about 10 years and have always been efficient, knowledgeable and good value, this has just stumped them and will be interested to know what I find out.

[Old Merc]

stevieturbo said:

Old Merc said:

The garage who did the job is responsible, it may just need the ECU resetting? Trouble is the only guys who can do it is a Mercedes Specialist.
The genuine Merc` kit is far more sophisticated than any of the diag tools local garages have.
You should inform your garage that the car is going to the Merc` man and you want them to pay the bill.

How do you know they are responsible ? Are you privvy to some other facts here ?

And any decent diagnostic gear you'd expect any garage to have would be able to communicate with all the modules necessary. Any competent garage doesnt use a £10 plug/adapter and phone app you know.

Looks like I have worded things very poorly. What I was trying to say was the original garage was responsible because they did not have the correct Merc` diagnostic gear. I bet all it will need is a Merc` man to plug in and reset everything.
I`ve had this with my 1997 R129, warning lights on, various things not working, all it needed was a few minutes on the diag` tool.

Edited by Old Merc on Monday 7th January 10:48

[stevieturbo]

Plenty of diagnostic kit available for them, even if your chosen garage doesnt have anything suitable.

https://www.scantool-direct.co.uk/mercedes-and-sma...

http://www.cardiagtool.co.uk/wholesale/mb-star-dia...

http://www.obd2shop.co.uk/wholesale/mb-star-diagno...

[Finn66]

Hi, I just thought I'd give an update on my problem with the transmission. It turns out that the car going into limp mode was a coincidence and nothing to do with the fitting of the new catalytic converter. The Mercedes expert read the car's faults and found the problem to be a switch inside the gear selector module. Luckily, he knew that this part could still be ordered direct from Mercedes for my model/year rather than having to order and replace the whole module which would have been very expensive. So, the part was ordered and fitted yesterday and the car is driving and changing gear as it should. The fella who read the codes/faults and carried out the repair is based in Godstone, Surrey, if any one wants his contact details, just reply to this thread.

[Sheepshanks]

Thanks for the update.

If the guy you used is a Mercedes specialist, is he in the wiki? https://www.pistonheads.com/gassing/topic.asp?h=0&...

[stevieturbo]

Good result.