P0299 Turbocharger/Supercharger Underboost Condition

P0299 means the turbocharger or supercharger system is producing less boost than expected. The module commanded or expected pressure that the engine did not achieve.

Code details

Generic OBD-II · P0

System: Fuel / Air
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace the turbocharger before pressure-testing the charge system and checking boost-control command versus actual response.

Symptoms of P0299

Check-engine light on, sometimes with rough or uneven running.
Hesitation, surging, or a noticeable change in fuel economy.
Occasionally hard starting or a smell of unburnt fuel.

Common causes of P0299

A failing or contaminated sensor (MAF, MAP, oxygen or air-fuel sensor).
Intake or vacuum leaks, or an exhaust leak near an upstream sensor.
Wiring, connector, or fuel-delivery problems that skew the reading.

Useful checks before replacing parts

Inspect charge pipes, intercooler, clamps, diverter or bypass valve, wastegate control, and vacuum or boost-control hoses.
Compare desired boost with actual boost, MAF data, MAP data, and throttle position under the same load that set the code.
Check for exhaust leaks before the turbine, restricted intake or exhaust, actuator faults, and turbocharger mechanical wear.

Related OBD-II codes

These nearby fuel / air entries can help compare wording and pin down the fault area.