Boost pressure regulation Control not reached P0299

[Aaron1875]

Vehicle has 150 k miles and I believe I’m running the original turbo but can’t be sure because don’t have full paperwork. I bought it in 2017 at 120 k. It was a one owner car that allegedly was covered on the good garage scheme by previous owner but trader did not pass on all the service history work and

invoices.

It went into limp mode over weekend (but did not trigger MIL light). This only occurred once on motorway giving it some up a gradient on the M62, I pulled over and restarted car reset and it drove fine pulling in every gear. I read the codes when I stopped and it threw up this P0299 code, and I cleared it. I have driven a further few hundred miles without it triggering the limp mode but it’s thrown up fault code again when reading VCDS. I cleared code and performed some output tests with vehicle off and could see Boost control valve operating duty cycle and some figures changing when it switched on and off and the same with EGR, but I’m ignorant to what the info means. I have attached pics at bottom of post.

I looked at VCDS Live data in basic settings having read some posts about looking for difference in manifold atmospheric pressure and Turbo exhaust pressure. When revving the car, VCDS indicate that absolute pressure atmospheric pressure is consistent (2nd measuring block in row 2 and the Turbo boost (first measuring block) occasionally goes up to 2.3 bar, however i noted that it fluctuated intermittently not reaching the desired pressure It’s hard to determine this when driving because the Alhambra manages up get up to speed but there may have been flat spots when gearing up however these 140 2.0 tdi BRT’s can be a bit laggy below 1.5 to 2k before boost builds and turbo kicks in.

What’s likely fault

N75 control valve ?

Torn diaphragm in the Diverter / wastegate valve ?

Vacuum leak ?- if it’s a vacuum leak it may explain the recent Brake warning light I have been experiencing (despite no brake loss issue), along with a random cooling warning light -(temp normal water level normal) VCDS reading indicates no issues ?
Would a boost leak in the Intercooler pipes also trigger this ?

I have attached pics of EGR output tests and boost valve output test with vehicle off. I would really appreciate someone translating them.

I have also attached the ECM engine module fault codes that show freezes frame data when fault triggers.








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[Crasher]

What is the cars VIN?

[Aaron1875]

Sorry for the delay been at office,

its VSSZZZ7MZ7V502162

thanks in advance

[Aaron1875]

VSSZZZ7MZ7V502162

Also I attempted data log and took a screen shot of a short drive up to 2nd gear to third and it felt like there was a healthy amount of boost, engine pulled nicely.

I have taken it on longer stretch of road and got up to 4th and could see boost reach 2.5 however I’m yet to try this in 6th gear but need an extra person to monitor data and pause the data/graph log.

What does this graph tell you ?

[Aaron1875]

Here’s a clearer pic of data log

[Aaron1875]

This is data log pulling from 3rd to 6th gear upto 70 odd mph. The car seems to be pulling fine. After returning home checked fault codes and the boost regulation code hasn’t returned.
As afore mentioned last Friday it went into limp mode whilst I was footing it in 6th gear, climbing a gradient up the steepest part of M62-which is the highest motorway in UK. Do you think that the atmospheric pressure differential was so great that it caused a massive difference between atmospheric pressure and required boost pressure, causing extra load on turbo thus triggering the boost regulation issue ?, or do you think it’s caused by a vacuum leak of some kind ?

[VAG-Abound]

Not atmospheric pressure. Firstly the difference is very small at the heights we have, and 2ndly the ECU has different maps for low ambient pressure based so would compensate even if on the Alps.

[VAG-Abound]

Can't really see which line is which in the pictures. If you're OK with Excel then just log the data while driving as far as you need and then draw your own graph from the CSV later on.

[Crasher]

You have a BRT code engine with SCR, I suspect the catalyst in front of the DPF is blocked.