What's led me here is a problem with my caddy. 2013. 1.6 tdi 102 remapped to 140, no issues for 3 months since remap.
Pulling out of a junction in 2nd slowly, probably should have been in 1st but stuck with it, all of a sudden engine management light on and into limp mode. Ignition cycle didnt cure it...revs limited to around 2000 rpm.
Fault code reader P0299 turbo underboost condition (words to that effect). Erased fault, road test and still the same. On a whim, I changed the n75 valve. No change.
Checked all vacuum pipes...ok and no leaks.
Diaphragm on turbo holds vacuum at around 20 inches of mercury, does not leak and operates control rod to turbo VNT.
Dismantled turbo, VNT ok and all mechanically sound.
Found EGR cooler mechanical flap controlled by vacuum seized....replaced and rebuilt all. Still no boost.
No other fault codes.
No air leaks on boost side.
All measured values appear ok for other sensors.
Air intake clear. MAP sensor swapped with a known good one...no change.
No air leaks heard....I.e. boost pipes off to inter cooler etc. All ok.
I'm clutching at straws now and dont know which way to turn.
Can anyone help?
Many thanks.
Laurence