P0299 Underboost Code Help

[RKrall]

Does the P0299 Underboost code only mean that your turbo needs to be replaced? I have a 2018 Sonic with this code and the mechanic that I take it to said that when this code comes up the only thing that it means is the turbo is bad and needs to be replaced.

 

[shorebreeze]

Not necessarily. I had a 0299 a couple years ago when I was out of town for reasons that were never quite clear. The turbo was intermittently not working, leaving things to the engine alone, and yet there weren't any obvious signs of issues, no oil seeping out from the feed line, no sign of play in the waste gate pin. It could have been my attempt at flashing the firmware on my ECM with a tune, or a radiator air lock temporarily shutting the turbo down due to overheating. So the first mechanic I took it to duly found that 0299 code and said I needed a new turbo, another mechanic I went to for a second opinion told me not so fast and while he was too backed up to deal with it, that I should immediately go to the nearest GM dealer, which I did after reversing the firmware flash, and the GM dealer ran the diagnostic and found the code had cleared, the turbo was running normally again and there was no indication of trouble.