Glow plug still flashing and limp mode

[karllap]

Hi,
I have a 2008 2.0 tdi A6 that keeps going into limp mode and the glow plug flashing and giving error P0299
Its a little weird, if I drive it nicely and let it slowly climb up the rev's when it gets to about 2 1/2k it goes, quick turn off and on then its fine again.
However, if I stick it sport or tip-tronic and thrash it up the rev counter it seems to be ok

Today I have cleaned the EGR and throttle body, changed the actuator in the inlet manifold and also replaced the inlet manifold as a local breaker had one for £20 so thought I may as well change that just in case whilst its in pieces. However still the same

Any body got any other ideas?

[L3g10n4rU]

Did you check the turbocharger?


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[Crasher]

16683(P0299)- Boost Pressure Regulation: Control Range Not Reached


it isn’t weird, it is probably the second most common question on any forum to deal with VAG turbo Diesel engines, hopefully this will proportionally decrease in direct correlation to the number of these automotive atrocities that are taken off of our roads and scrapped. Your turbo is not reaching its full boost potential and for some unknown reason the EU thought they should make this a limp mode issue as with over boosting, presumably as the issue causes soot which kills people.

[karllap]

Thanks for the replies, what I meant by weird is that it seems to be ok if I drive it one way but not if I drive it another. I'm guessing its not the turbo as it spins up ok when thrash but happy to be corrected.
I was wondering if it points at a sensor, EGR valve or something like that?

[L3g10n4rU]

If you have vcds, open the turbo mvb and drive the car the way it takes limp mode. If the turbo boost drops at 2000-2500 rpm, its the turbo. Your car enters limp mode at 2200 rpm from my experience. Standard mode means turbo acts as normal. Tiptronic or sport mode gives better boost on the turbo itself, and that is ehy you don’t get limp mode in this situation. Check your turbo mechanically, but most of time it’s the electronic part, it costs you no penny. I can tell you how to test turbo with vcds if you don’t know.


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[Crasher]

This fault code is usually due to a loss of vacuum control to the turbo actuator and on this particular model I have had a number of them where one of the wires to the N75 valve under the exhaust manifold snaps due to heat damage, you can only see this from below.