What does this code mean?
A turbocharger or supercharger helps push more air into the engine. P0299 means the resulting pressure was lower than expected. A leak or control problem can also cause this result; the code does not prove the turbocharger is broken.
Locate the reported problem
Underboost can appear with reduced power. Identify the engine and boost-control design before interpreting a pressure value.
Read it with the other codes
P0234 concerns excessive boost. For P0299, a leaking charge-air connection, a control problem and an incorrect pressure signal lead to different tests.
Possible causes to investigate
These are possibilities, not a diagnosis or a ranked list of failed parts.
- A leak, restriction or pressure-measurement problem in the air path.
- Boost-control behavior involving an actuator, valve, its supply or the turbo mechanism.
What to do first
- Save all codes and note when power drops: during acceleration, uphill or after warming up. Record any unusual noise or smoke.
- With the engine off and cool, report visible loose air connections without dismantling the turbo. Do not adjust an actuator or deliberately reproduce overboost.
What the workshop can check
Compare requested boost with measured pressure under the correct test conditions, then assess the air path, pressure signals and control mechanism. A turbo replacement needs evidence beyond a boost code.
A useful question to ask
Does the pressure shortfall come from an air leak, the control system or the measurement?
Your vehicle changes the next step
Year, make, model, engine and the complete code list matter. Cylinder layout, test conditions and repair procedures can differ. Use service information for the exact vehicle; a generic code does not establish an exact failed part.
Can I keep driving?
This page cannot decide whether your car is safe to drive. A flashing engine light, severe shaking, overheating, strong fuel smell or major power loss calls for prompt attention. Stop safely when needed, follow your handbook and seek assistance rather than continuing a test drive.
Terms in this guide
These words appear in the explanation. Select an underlined term in the text to reach its definition.
- Turbocharger, supercharger and boost
- A turbocharger uses exhaust energy to compress incoming air. A supercharger can be powered another way. Boost means supplying air above ambient pressure.
- Control unit
- A car computer that receives measurements and controls the engine or another system. It may also be called a module, ECU, ECM or PCM.
- Sensor and signal
- A sensor measures something such as pressure or temperature. Its signal carries that information electrically to the car computer; a wrong reading does not always mean the measured component is faulty.
- Actuator and solenoid
- An actuator turns a control command into physical action. A solenoid uses electricity and magnetism, for example to move a valve.
Sources and scope
Definitions and general OBD context are cross-checked against the references below. Manufacturer documents describe specific vehicles and systems; their procedures and thresholds are not instructions for every make. This is educational guidance, not a vehicle-specific repair procedure.