P0299: Turbocharger or supercharger A underboost condition

● Fix soon
Usually drivable for a short time, but check it soon. It can get worse.

Boost pressure is below the target. The driver may notice weak power, especially when accelerating, and possibly limited power mode.

Guided check

  1. Is there a split or loose turbo hose?
    If yes: Repair it, clear the code and road test.
  2. Does the wastegate or actuator stick or fail to move?
    If yes: Check its vacuum or electric control before replacing the actuator.
  3. Is there shaft play, oil in the hoses or a blocked exhaust?
    If yes: Inspect the turbo and exhaust before quoting. Check the oil supply if the turbo has failed.

These checks are general and are still being reviewed by working mechanics.

Causes vary by car. Test before you order a part.

Likely causes, most common first

  • Boost leak in a hose or intercooler
  • Faulty wastegate or actuator
  • Worn turbo
  • Blocked air filter or exhaust restriction

Parts usually involved

Test before you replace

Pressure test the intake side for boost leaks and compare actual boost with target before condemning the turbo.

General guidance for generic OBD2 codes. Always follow the maker's procedure for the car in front of you.

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