P0299Powertrain
Powertrain · SAE
Turbocharger Underboost Condition
Meaning
Boost pressure is below the value requested by the ECU. The turbo is not producing the expected boost (underboost).
Common causes
- Boost leak (split hose, intercooler, loose clamp)
- Variable geometry (VGT) stuck or actuator seized
- Faulty boost-control solenoid
- Restricted intake or exhaust (e.g. clogged DPF)
- Wastegate stuck open
- Worn turbocharger or damaged bearings
Symptoms
- Marked power loss
- Limp mode
- Sluggish acceleration
- Check-engine light on
- Possible whistle or hiss from an air leak
Severity
High: the vehicle loses power and may enter limp mode, severely reducing performance.
What to do
- Read live data: desired vs actual boost pressure
- Inspect the boost system (hoses, intercooler, clamps) for leaks
- Check the variable-geometry and actuator movement and the boost-control solenoid
- Check the intake and exhaust (e.g. DPF) and the condition of the turbocharger