P0299
CAUTION
Turbo underboost
The turbo is not making the boost the engine asks for.
P0299: The turbo is not making the boost the engine asks for. Caution: you can keep driving carefully, but the engine may derate; get it addressed soon.
Mechanical · Air intake / Turbo
What it means
Turbocharger underboost condition. On diesel trucks it is almost always a charge-air leak or a stuck variable geometry, and it shows up with power loss and black smoke.
Most likely causes
Charge-air leak between turbo and cooler
Very likely
Variable geometry stuck with soot
Very likely
Plugged air filter
Likely
Exhaust leak ahead of the turbo
Likely
Tests, cheapest and most decisive first
1. Pressurize the charge-air system
Expected result: Holds pressure with no audible leak
Tool: Pressure test kit
2. Check air filter restriction
Expected result: Within specification
Tool: Restriction gauge
Read it off your own dash
Take one photo and DERATE tells you whether you can keep driving.
DERATEDERATE assists. It does not replace inspection by a qualified technician.