P0299
UniversalTurbo / Super Charger Underboost
The engine control system has detected less turbocharger or supercharger boost pressure than expected. Boost helps the engine take in more air; underboost can reduce power and may affect drivability. This code identifies a detected condition, not proof that the turbocharger or supercharger itself has failed.
⚠️ Before You Begin (Safety First)
Avoid hard acceleration until the cause is understood. Stop driving and arrange assistance if the vehicle has severe power loss that makes it unsafe, heavy smoke, unusual loud mechanical noises, overheating, or an oil-pressure warning. Do not touch hot or moving engine components.
Common Symptoms
- Reduced engine power or slower acceleration because the engine is receiving less boost than expected.
- The engine may feel weak under load; the extent can depend on how far boost is below the expected level.
- The check-engine light may be on, and other symptoms may be absent.
- Some vehicles may enter a reduced-power mode in response to the detected condition.
Common Causes
- A leak or loose connection in the intake or pressurized charge-air plumbing can let boosted air escape.
- An exhaust leak or restriction can interfere with the energy or flow needed for boost, depending on the system.
- A boost-control valve, wastegate, bypass mechanism, actuator, or its control circuit may not operate as intended.
- The turbocharger or supercharger may have a mechanical problem, but this code alone does not establish that it has failed.
- A pressure or airflow sensor, its wiring, or its connections may provide inaccurate information used to assess boost.
- An intake restriction, such as a clogged air filter, may limit airflow.
Diagnostic Steps
- Record any other diagnostic codes and available freeze-frame information before clearing codes; related information can help show when the condition occurred.
- With the engine off and cool, visually inspect accessible intake and charge-air hoses for loose connections, cracks, or obvious damage.
- Check the air filter and accessible intake ducting for an obvious blockage or disconnection.
- Look for loose or damaged electrical connectors at accessible boost-related sensors and controls; do not probe circuits without vehicle-specific information.
- If no obvious issue is found, have the vehicle assessed using model-, year-, and engine-specific diagnostic information rather than replacing a component based on this code alone.
When to Call a Professional
A technician can compare commanded and measured boost using scan data, check sensor readings for plausibility, and inspect the intake and charge-air system for leaks or restrictions. Further checks may include the exhaust path, boost-control system and actuator operation, and turbocharger or supercharger condition. The exact tests depend on the vehicle.
Compare component listings
Confirm diagnosis and vehicle fitment before buying. A listing does not prove that a part needs replacement. We may earn a commission from qualifying purchases.
Commonly Asked Questions
Does P0299 mean the turbocharger or supercharger must be replaced?
No. It indicates that boost was detected below the expected level. Leaks, restrictions, control-system problems, sensor information, or a mechanical fault may contribute, so diagnosis is needed before selecting a repair.
Can I keep driving with P0299?
If the vehicle runs normally, cautious driving to a repair facility may be possible, but avoid hard acceleration. Stop and seek assistance if power loss makes driving unsafe or if heavy smoke, unusual mechanical noise, overheating, or an oil-pressure warning occurs.
Can a boost leak cause this code?
Yes. A leak in pressurized intake or charge-air plumbing can allow air to escape, contributing to lower boost than expected. Visual inspection may find obvious damage, but some leaks require suitable diagnostic testing.
Why might the code appear without obvious symptoms?
The detected boost difference may not be noticeable in every driving condition, or its effect may be mild. The engine control system can detect a condition even when the driver does not feel a clear change.
Browse Available Code Guides
Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.