Hello everyone I'm new here. I acquired this very clean example from a dealer up north (newcastle, sadly 120+ miles from where I live)

2016 2.0 TDI Technology estate

70k miles, cambelt & pump and service done just before I picked it up

Now for the problems. I tool it on it's first long run and after about 100 miles it started to go into limp mode. No power, turbo won't kick in, won't go above 2500 rpm. I decided to carry on to my campsite about 30mins then called the breakdown. They put the machine on it, said it was the DPF pressure diff sensor, cleared the codes and it worked again. Until it didn't. On the way home same thing happened again. I took it to garage who put their machine on it. They said there were no errors. Very strange and it had been happening on and off all the way back and to the garage. It seems to be fine for a bit then starts to happen seemingly randomly. Anyway, they changed the sensor as that was the code that was showing previously and did a forced regen on the DPF. All seemed fine for a couple of weeks then it started happening again. Not on a long drive this time just before a long drive on the way back from the fuel station after just filling the tank. I was due to do 500 miles over the next 2 days and luckly I hadn't set off yet if not a bit annoying.
It went into limp mode 3 separate times over the last week. On both slower roads and a bypass. No rhyme not reason to it seemingly and most annoying, zero dash lights or codes logged in the computer. I took it to the garage who replaced the part and they put it on their machine again today and said the codes were completely clear.

How can a car that puts itself in limp mode not be recording the error that caused it?

Has anyone seen this type of thing before? Please help me, it's driving me nuts. Any advice welcome. I think my only option here might be to give it back to the dealer and make it not my problem any more.

Mercedes are very prone to that sort of behaviour, along with showing no codes at all, when they have a failing EGR valve.

Although, if you’re considering handing it back, then just do so without dragging your hurt on any further.

70k on a 10year old diesel is not enough mileage for the emissions systems to be happy.

I’d lay money that the egr valve is sticking open, probably clogged with soot from hundreds of short journeys over the last decade.

18 hours ago, mac11irl said:

70k on a 10year old diesel is not enough mileage for the emissions systems to be happy.

I’d lay money that the egr valve is sticking open, probably clogged with soot from hundreds of short journeys over the last decade.

Don't you think if it was the ERG sticking and causing the limp it would log the error? Seem bonkers if not.

I've got VAG DPF so have started monitoring it to see if I can spot something amiss when it's happening.

From the look of the MOT's this car did about 6-7k miles per year pretty consistently.

Might be worth doing an Italian tune up somewhere clear and safe

If that doesn’t work and you gut is saying take it back then listen to your gut!

I’ve got a 2016 too and only do around 3k a year, but when I do use it, it’s for 4 hour journey at a time, semi spirited 🤪

2 minutes ago, Danoid said:

Might be worth doing an Italian tune up somewhere clear and safe

If that doesn’t work and you gut is saying take it back then listen to your gut!

I’ve got a 2016 too and only do around 3k a year, but when I do use it, it’s for 4 hour journey at a time, semi spirited 🤪

What is this Italian Tune Up you speak of? Sounds interesting. Haha.

I only bought this car for long journeys where I have to do anywhere between 400-500miles over the space of 2 or 3 days about once a month. Oh, and the off tip run.

Italian tune up is basically giving it a quick thrashing.

Obviously make sure engine is warm first!!, then go no higher than 3rd gear around bendy roads with some straights (can be hard to find suitable roads I know)

Once warm you need to drive rather horribly, like in 1st accelerate slowly to near red line but keep it in first, then the same for 2nd gear, repeat several times

then stop somewhere and floor it but make sure it doesn’t go higher than 3rd

Repeat that flooring too

If that all works and car doesn’t go into limp mode then you might have cleared EGR enough, if the above just doesn’t work then could be EGR is too caked in crap.

Also the Italian tune up method is more of a preventative measure, but might just help clear a little bit to know that the EGR needs a proper clean

Sounds like a good laugh at least. I'll give it a shot

Took it out for a "tune up" today. As you said flooring it multiple times. Keeping the revs high. Never above 3rd etc. Didn't seem to make any difference. Limp mode seemed to kick in after about an hour going up a bypass (last pic) The dpf was trying to do a regen. Strange thing is, a couple of days before I'd noticed the soot mass jump from about 10g to 23g almost instantly (first 4 screen shots) I've got a screen shots from vag dpf.

Ah that sucks, at least it was free to check.

Unfortunately I don’t know much about DPF’s and how to read the measurements, but your car was good until it done a regen and then that’s when the limp mode happened?

That's what seemed to happen yeah. It wasn't as soon as the regwn started but it was certainly while it was happening. This would explain why it only seems tk happen every now and again. Unfortunately I just can't have a car where it's basically unusable every 100miles or so.