Underboost issues.

[Jibber]

Hi guys, I don’t post much, bit of a lurker. But I thought I’d reach out to see if someone might be able to help me with my friends bi-turbo amarok (I forget what year it is but will update when I’m closer to the vehicle) that keeps going into limp mode and throwing P02CB turbo underboost condition code. I’m a mechanic so he bought it to me after losing faith in the previous workshop. I don’t have a lot of experience with these cars but I said I’d do my best.
The previous shop has replaced the two boost control solenoids, removed turbos and inspected them for wear and checked wastegate actuators, leak tested intercooler plumbing, checked the dpf and exhaust for excessive back pressure and tested the harness for open circuits etc...

All of the above seems pretty logical, so I have started by inspecting the egr and ecu connectors but everything looks very clean and well looked after. My scan tool isn’t showing live data very well so I’m struggling to monitor map sensors and alike.

So I did some googleing and not coming up with a lot of information. Any advice or experiences would be appreciated

Cheers J

[Lucas_R]

I had a P02CB error in my Audi SQ5 (biturbo TDI) about 7 months ago. Mine was caused by a ecu tuning mishap but basically my DPF’s were not regenerating as normal and they ended up getting so clogged up with soot that it prompted the P02CB error and very shortly after that, limp mode.

I had to physically remove the 2x DPF’s off the car (thankfully very quick to remove and replace) and backflush them out with my gerni and a mixture of degreaser and brake cleaner. A huge amount of crap came out of the DPF’s.

I then used VCDS (VW/Audi diagnostic software) to tell the car that the DPF’s were replaced which reset all of its soot settings etc. Then got my ecu tune fixed and havent had an issue since.

Some of that saga here: Playing with an Audi SQ5 TDI

Can you use your diagnostic scanner to check soot levels on the car?

[Jibber]

Thanks Lucas, yeah I checked the pressure difference at the pressure sensor in live data and it’s telling me there is no back pressure at all, and I’ve checked the dpf visually with a borescope but not not physically removed it and had a good look. Thanks for your reply man, something for me to think about.