P0299 The OBD-II code P0299 signifies a "Turbocharger/Supercharger A Underboost Condition," meaning the turbocharger isn't producing enough boost pressure for the engine. This is often caused by a leak in the boost system, a faulty turbocharger or actuator, a restricted air filter or diesel particulate filter, or a bad boost pressure sensor. Symptoms include loss of engine power and an illuminated check engine light. This video explains how to diagnose and fix a P0299 code: Common causes of P029