TDI 170 Engine warning light comes on at high speeds/load

[nafets]

High all! My Passat 2.0 TDI 170 is playing up slightly.
On my way back from Holland a few weeks ago the check engine light came on and power was reduced. It happened when driving at 120+ mph for most of the way. I pulled over and restarted the car, worked fine since.
Last week on my way too and back from Cornwall it happened again but this time at lower speeds but on hilly roads. Again power reduced but no other alarms. Restarted and fine since.
What could cause this fault only when the engine load is very high, on flat roads and below 95 mph it doesn't happen. I suspect a sensor being dirty/faulty.
I am not keen on getting it to a dealer as they will charge £60 for a readout.
Your views please
Cheers
Stefan

[Guest 2]

Look at the user map link in my signature and I'm sure someone is near with the correct kit

No point in guessing until a scan is done.

[RichardSEL]

Come up the A102 to Sun in the Sands roundabout and I can do a readout for you.
Not a diesel head here so you'll have to take its info to someone who knows TDI 170s
But at least it'll tell more. DPF regeneration? Been running supermarket Derv?

Otherwise the map is at: VWAF User Location Map - VCDS - Google Maps

[DSG4ME]

That's most likely dirty turbo veins,

Here's the options

Take it off and clean it, this doesn't always sort it btw or it returns soon after,

Take it to the motorway late at night and beans it through to 3rd gear and hold 3rd to 4k rpm, do this three or four times and hopefully it will unstick them, as yours has a dpf I don't suppose you see black smoke in the mirror do you? if you do, beans it as described until you don't see any smoke.

[nafets]

Gents
Many thanks for the feedback and VCDS readout offers!!
Don't think it is DPF regeneration as it happened 3 time so far, hours into a long journey. At rather high speeds, so the passive regeneration should do the trick just on the exhaust gas temperature alone.
Fuel is the normal BP diesel and no signs of black smoke. The fact that the fault clears and stays away when I restart the car is strange. I have not been able to replicate it after I restarted the car, no matter how fast I drove afterwards.
RichardSEL
I won't be in the area anytime soon, but would like to keep your "offer" warm
Cheers
Stefan

[martin1810]

Quote "The fact that the fault clears and stays away when I restart the car is strange."
No it isn't. This is normal for a turbo fault. A fault code read will almost certainly say 'over-boost'.

[nafets]

Hi Martin
Many thanks for the reply.
Given the fact that the "system" resets and runs fine for many miles afterwards, can I conclude that it is likely the MAP sensor that is on its way out? Can it be cleaned? OR is it likely to be mechanical, ie turbo actuator not travelling freely enough due to continues running in max vane position.
I find it really strange that the cars runs like a dream when driving normally up to 95 mph. It only starts playing up at near max speed or when the motorways become hilly and driving at 90-95 mph.
Your expert thoughts are more then welcome
Stefan

[martin1810]

You have classic sticking turbo vanes symptoms. Prolonged high speed runs cause the vanes to rest in one spot. As you lift off rpm the vanes remain in place instead of moving. This causes an 'overboost' spike and the ecu drops the engine into limp mode. Switching off/on resets the ecu. Turbo boost is one of the few faults that can be reset in this way. Try driving with lots of rpm like a petrol engine car. This may help clear up the sticking.

[nafets]

Thanks guys!
Seems like I will be spending some time cleaning the turbo this weekend.
Cheers
Stefan

[jamescking]

I had the same issue with mine a few months ago, took it back to the dealership I got it from and they replaced the turbo as it was still under their warranty, works like a dream now.