P0299: Turbocharger/Supercharger A Underboost Condition

Common causes

• A boost leak: loose clamp, split intercooler hose or cracked intercooler
• A sticking wastegate or wastegate actuator
• A faulty boost pressure sensor
• A worn turbocharger
• A clogged air filter or exhaust restriction

Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.

Symptoms

• Loss of power, especially when accelerating
• Reduced-power or limp mode
• Whistling or hissing under boost
• Check engine light

Is it safe to drive?

You can usually drive gently, but power will be limited. A sudden loss of power can be unsafe when merging or passing.

How to check it with a scanner

1. Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
2. With the engine off and cool, check every intercooler hose and clamp for oil residue or looseness.
3. Compare desired and actual boost in live data during a safe, legal acceleration (with a passenger watching the scanner).
4. Check the wastegate linkage for free movement and inspect the air filter.
5. After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.

A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.

Questions

Related codes

• P0101: MAF sensor reading out of range
• P0106: MAP sensor reading out of range
• P0087: Fuel pressure too low
• All trouble codes
• How to choose a car diagnostic scanner