P0299: Turbocharger/Supercharger "A" Underboost Condition
The turbo or supercharger is not making as much boost pressure as the engine computer is asking for.
What P0299 means
P0299 means the computer requested a certain amount of boost and the sensors say the turbo or supercharger did not deliver it. RepairPal lists causes such as an exhaust leak, a failed MAP sensor, a bad control solenoid, a failing turbo and wiring problems. In practice, boost leaks are one of the most common causes: a split intercooler hose, a loose clamp or a cracked plastic pipe lets pressurized air escape before it reaches the engine. A wastegate stuck open or a boost control solenoid that does not work will also limit boost. An exhaust leak before the turbo robs it of the energy it needs to spin up. Many cars cut power to protect the engine, so you may notice the car feels much weaker than normal. KBB says to see a mechanic soon, especially if the turbo itself has failed. Shops pressure test the intake for leaks, command the wastegate with a scan tool and inspect the turbo for shaft play or oil leaks.
Common symptoms
- Check engine light on
- Noticeable lack of power
- Reduced power or limp mode
- Increased fuel consumption
- Whistling or hissing from a boost leak
Most common causes
- Boost leak from a cracked intercooler, hose or loose clamp
- Wastegate stuck open
- Faulty boost control solenoid
- Exhaust leak before the turbo
- Failing turbocharger
- Faulty MAP or boost sensor
What to check yourself first
With the engine off, check intercooler hoses and clamps for oil residue, splits or looseness; oil on a coupler often marks a leak. Listen for a whistle or hiss when accelerating. Check the vacuum lines to the wastegate actuator.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace intercooler or boost tube | $609-$683 | Boost leaks at intercooler pipes and couplers are a very common cause. |
| Replace boost control (wastegate) solenoid | $206-$241 | If the control solenoid is not commanding the wastegate closed. |
| Replace boost pressure sensor | $236-$273 | When the sensor reads low but real boost is fine. |
| Replace turbocharger | $2,631-$3,261 | If the turbo has worn bearings, damaged blades or heavy oil leaks. |
| Check engine light diagnosis at a shop | $125-$183 | Includes a boost leak smoke or pressure test. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0234 Turbocharger/Supercharger "A" Overboost Condition
- P0106 Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance
- P0101 Mass or Volume Air Flow "A" Circuit Range/Performance
- P0171 System Too Lean (Bank 1)
- P0401 Exhaust Gas Recirculation "A" Flow Insufficient Detected