Slight loss of power, Lots of white smoke..

[marclej]

ello fellas.. I baught a 2006 a3 tdi 170 s-line back in January and up until now it has been great .. Roughly a week ago the emmisions light popped up on the dashboard so I took it to my mechanic who is pretty handy when it comes to vw/audi he plugged it in and told me there was a fault 'P0473 exhaust pressure sensor high.. Due to working 5 days a week and him not being available weekends I told him I'd book it in when I can sort something out.. a few days later the car went into limp mode , was driving sensible at the time wasn't hammering it if I remember correctly I was doing about 40ish in 4th gear.. After turning the ignition off and back on the car was ok again.. boosting fine driving like it always has.. then the next day limp mode again .. but since then I've noticed a lack of power.. not as slow as limp mode but just noticeably a bit less powerful than usual.. I just put it down to being related to the exhaust pressure sensor .. tonight I took the car out to give a friend a lift.. After getting into the street and turning I noticed insane amounts of thick white smoke coming out of the exhaust.. literally smoking the street out.. people coming out of their houses for a look it was embarrassing.. I turned the engine off after about 20 seconds of the smoke coming out.. started it back up drove off and noticed the car felt more powerful.. and the smoke had stopped belllowing out .. it felt as IF the slight loss of power I'd been having was gone .. was pulling as it should be .. though I think I could hear a slight hiss like air being blown as the turbo was boosting though I've heard this a few times before ..
Panicking my *** off I told a neighbour about it and he brought his laptop down and plugged the car in to see if anything would show up which could be related .. I've had the white smoke happen before but this was in February time and only happened the once but it was exactly the same as tonight .. except for the power loss prior to the smoke .. so yeah he plugged it in here are the fault codes..
P0473 - exhaust pressure sensor high - permanent

P0471 - exhaust pressure sensor range / performance - intermittent

P0299 - Turbo / supercharger underboost - intermittent

Any advice would be greatly appreciated.. as im baffled by the white smoke happening randomly and then being completely fine afterwards

 

[aqibi2000]

Check for intake air leaks regarding the underboost, perform a vacuum test too

 

[marclej]

Roger that.. could the pressure sensor and the smoke be related to the dpf? as for the last few months I've only been driving back and fore work and over to my parents .. 15 minute journey at most and not the kind of roads to get the temp up for a dpf regen.

 

[aqibi2000]

Dpf has dedicated sensor to read if it's full or requiring regeneration. I would rule that factor out since when the g450 fails the dpf light would be on the dash.

 

[marclej]

Dpf lights just come up on the dash now in orange.. worth taking it for a blast on the motorway do ya think ?

 

[aqibi2000]

Get someone to plug in VCDS get the error codes

Also read the SOOT mass blocks in the engine blocks. G450 is a very common failure irrespective to your situation