P0299: Turbo/supercharger underboost
The turbo is producing less boost than requested. The engine may go into limp mode.
Updated
What P0299 means
A turbocharger uses the exhaust to push extra air into the engine. The engine computer asks for a boost pressure and checks it with a boost pressure sensor.
When the measured boost stays below what it asked for, it stores P0299 and often limits the power, so the turbo isn’t pushed harder to make up the difference.
Read My Car’s live data shows the intake manifold pressure and the barometric pressure, if your car reports them. The difference between the two is the boost.
Can I keep driving?
Check soon
Probably OK to drive short-term, but have it checked soon. Fuel use or emissions may be worse.
General guidance based on the code alone, not on the car’s actual condition. If in doubt, stop and ask a mechanic.
Limp mode makes overtaking and joining fast traffic harder: drive with that in mind until it’s fixed.
Symptoms
- Noticeably less power, especially when accelerating.
- Limp mode, sometimes until the engine is restarted.
- A hiss or whistle from a leaking boost hose.
Common causes
- Leaking boost hose or intercooler. A split hose or a loose clamp lets the pressure escape. Look for oily patches around the joints.
- Sticking turbo vanes or wastegate. Soot can make them stick, so the turbo can’t build pressure.
- Faulty boost pressure sensor. The boost is there, but the sensor doesn’t report it.
Typical fixes
- Check the boost hoses, clamps and intercooler for splits, loose joints and oil.
- Have the turbo’s vane or wastegate control checked for free movement.
- Have the boost pressure sensor and its wiring checked, and compare its reading with the barometric pressure with the engine off.
- Clear the code after the repair and check the power on a test drive.
Questions
Can I drive with P0299?
Probably for a short time, but have it checked soon. Limp mode limits the power, so allow for that in traffic.
Does P0299 mean the turbo is broken?
Not necessarily. A leaking hose or a faulty sensor sets the same code, and both are easier to check. Rule them out first.