Po299 , Traction control, Istop, low power
Cheers! Can confirm it's not an gearbox issue as mine is a manual and experiencing the same thing. Codes clear on their own once I shut off the engine. Turbo was checked, exhaust pressure pipe cleaned, MAP sensor replaced and DPF differential pressure replaced aswell. DPF was cleaned at a local shop but not taken off. Problem still persists. Had exhaust camshaft, vaccuum pump, HLA & lifters replaced. Had intake carbon clean, EGR valve clean and EGR cooler cleaned.
P0299 code and triggers limp mode occasionally when driving over 80mph. The engine runs on slightly higher boost levels due to a previous ECU tune.
Live data findings: turbo boost actual vs commanded have a 5psi discrepancy when during regular driving (<3000rpm) and doesn't read anything below 12.7 (actual lower than commanded, no vaccuum). During active regen, values come to normal, no discrepancy and vaccuum also noticeably improved: 8 psi achieved. Exhaust temps (sensor 1) drop down to as low as 94 degrees celsius (likely limp mode related) but the car can still redline, no loss of power noticed. Boost regulator valve has been recently replaced (but there are two of them, as far as I can recall).
To me it looks like there is not enough vaccuum at low RPMs to control the wastegates properly. Thought might be the vaccuum pump but mine was replaced about 25.000 miles ago. Curiously enough, the values always come back to normal during active regens (where injection timing and amount are re-adjusted by the ECU to increase exhaust temps and burn off soot).
I'm only left with two options: it's either vaccuum leaks or bad fuel injectors. The car is second-hand so I can have a guess maybe the previous owner used cheap fuel.
Have a look at your live data. I'll keep you updated on how it goes with mine and hope we get to the bottom of this soon.
Cheers
P0299 code and triggers limp mode occasionally when driving over 80mph. The engine runs on slightly higher boost levels due to a previous ECU tune.
Live data findings: turbo boost actual vs commanded have a 5psi discrepancy when during regular driving (<3000rpm) and doesn't read anything below 12.7 (actual lower than commanded, no vaccuum). During active regen, values come to normal, no discrepancy and vaccuum also noticeably improved: 8 psi achieved. Exhaust temps (sensor 1) drop down to as low as 94 degrees celsius (likely limp mode related) but the car can still redline, no loss of power noticed. Boost regulator valve has been recently replaced (but there are two of them, as far as I can recall).
To me it looks like there is not enough vaccuum at low RPMs to control the wastegates properly. Thought might be the vaccuum pump but mine was replaced about 25.000 miles ago. Curiously enough, the values always come back to normal during active regens (where injection timing and amount are re-adjusted by the ECU to increase exhaust temps and burn off soot).
I'm only left with two options: it's either vaccuum leaks or bad fuel injectors. The car is second-hand so I can have a guess maybe the previous owner used cheap fuel.
Have a look at your live data. I'll keep you updated on how it goes with mine and hope we get to the bottom of this soon.
Cheers
Last edited by calin_andrei_gabriel@yahoo.com; Dec 23, 2025 at 10:29 AM.
Just personally curious What program are you using and whom did this ECU/EFI Calibration?
Your response reads someone randomly changed ECU calibrations mappings
Sorry not going to debate this nor do i have any advice and your issue is not the same as the other members unless he returns to state he has a ECU calibrating program and what "exactly" was done in the way of calibrating. I have seen responses like this so often on many platforms having to do with issues and some "tooooner' uses a "band-aide" approach to calibrating a ECU.
Thread
Thread Starter
Forum
Replies
Last Post



