8R SQ5 TDI code P0299 Boost Pressure Regulation

[shterk]

Hi all,

As the title suggests I am having issues with my SQ5 with code P0299 showing up on vcds.

I have already replaced the N75 valve at the supply price of $200 (eesh) however this hasn't solved the issue (glow plug light on dash flashing).

Does anyone have any.suggestions as to what else it could.be? I'm hoping it's not a turbo issue, I.did have all 6 injectors just replaced by my mechanic due to a previous fault which cost me A LOT of money so not sure if.there is any correlation between these issues.

Vehicle is 2014 model and has done 160k kms if that helps, regularly serviced along with Liqui Moly added to fuel to help with DPF longevity.

Appreciate any help.

 

[shterk]

Latest is that a new fault code has superseded the one from above, there is now a “P22D5 00 Implausible Signal from 11866 - Position Sensor for Turbo Inlet Valve” that won’t go away and comes on every time I apply load on the accelerator pedal (coil light flashes on dash too).

For reference I have replaced the MAF, Charge Pressure Control Solenoid Valve (N75), Exhaust Gas Recirculation Cooler Changeover Valve (N345) and the Turbine Changeover Valve (N529) which have all been quoted as potential problems through various forums yet the issue still remains. I’ve tested the turbo actuator and it holds pressure as well as the vacuum unit that connects to the N529 valve (as per the workshop manual recommendation) so I’m at a loss as to what it could be.

An interesting observation whilst hooked up to VCDS was that the “Bypass valve for high pressure turbocharger turbine inlet” values would drop significantly from 99% to a value so low that the coil light would come up thus prompting the DTC as mentioned above. I believe there is a correlation between the two but can’t seem to work it out. I’ve checked the DPF level and it was high but after a forced regeneration the values came back down to suitable levels so I doubt the DPF is at fault but again I’m not sure.

I’d appreciate any advice anyone can give, over 100 views yet no-one has been able to offer any guidance!

 

[jnrdavo]

sorry, not heard of either of those ones, but I'm not a mechanic..

Just out-of-the-box thinking, have you checked your battery? How old is it? A few people on here have had what would seem totally non-relatable errors coming up in their car and a new battery has solved them.

Most likely not what you are seeing, but another box to check that you have checked this..

Looking at VCDS, your second error coould be a result of quite a few things..

18995/P2563/009571 - Ross-Tech Wiki

What was the error when you had to have the injectors replaced? Could this be pointing back to the original problem? Did the 'new' problem come up straight after the injector replacement?

I have the haynes manual for my S3. One of the online features is you can put in the error code and it will walk you through the steps to see if it can be narrowed down to the actual failed part. In my case, it showed all the diagrams and cable connections/relays etc and how to test them, what results I should be seeing etc..

 

[shterk]

Thanks for the response and suggestions.

I’ve checked the battery but that is fine so I can rule that one out. The symptoms prior to injector replacement was rough vibration at idle and low RPMs, there was no fault code that came up however upon research I found that there was an abnormally high injection quantity deviation reading on one of the cylinders (#3) that pretty much confirmed an injector related issue. Mechanic and diesel specialist recommended a replacement of all injectors which solved that issue however the vehicle didn’t even last a week before I started to experience the aforementioned problems.

All I know is that the high pressure turbo is not kicking in which potentially leads me to think that the electronic actuator (servomotor) that controls that turbo may be playing up.

 

[jattsta]

Thanks for the response and suggestions.

I’ve checked the battery but that is fine so I can rule that one out. The symptoms prior to injector replacement was rough vibration at idle and low RPMs, there was no fault code that came up however upon research I found that there was an abnormally high injection quantity deviation reading on one of the cylinders (#3) that pretty much confirmed an injector related issue. Mechanic and diesel specialist recommended a replacement of all injectors which solved that issue however the vehicle didn’t even last a week before I started to experience the aforementioned problems.

All I know is that the high pressure turbo is not kicking in which potentially leads me to think that the electronic actuator (servomotor) that controls that turbo may be playing up.

I think I had a similar code on my B9.
Dealer told me it was g31 sensor but it wasn't. One of the wires going to the sensor was fried.
Get a voltmeter and check resistance on each wire for all the turbo related sensors (N75, G31, MAF, MAP etc)
If you do find one wire doesn't have resistance, run a temporary wire and see if it fixes the issue.