P0234: Turbocharger/Supercharger "A" Overboost Condition
The turbo or supercharger is making more boost pressure than the engine computer allows.
What P0234 means
A turbocharger uses exhaust energy to push extra air into the engine, and the computer controls how much boost it makes by opening a wastegate or adjusting variable vanes. A boost pressure sensor reports actual boost back to the computer. RepairPal explains that P0234 sets when the boost sensor readings go above specification, or on some vehicles when knock sensors signal pinging during boost. Too much boost raises cylinder pressure and heat, which can lead to detonation that damages pistons and head gaskets. The usual causes are a wastegate that is stuck closed, a faulty boost control solenoid, a cracked vacuum line to the actuator, or a bad boost sensor or wiring. Aftermarket tuning can also trigger it. KBB says experts do not recommend continuing to drive. Shops compare actual boost on a gauge with the sensor reading, command the wastegate solenoid with a scan tool and check that the actuator moves. Fix it before driving hard again.
Common symptoms
- Check engine light on
- Engine pinging or knocking on acceleration
- Reduced power mode
- Hesitation or stalling
- Sometimes no symptoms
Most common causes
- Wastegate stuck closed or actuator failure
- Faulty boost control solenoid
- Faulty boost pressure sensor or wiring
- Cracked or disconnected wastegate vacuum line
- Knock sensor signal triggering the code
- Aftermarket tune or boost controller
What to check yourself first
Inspect the small vacuum hoses running to the wastegate actuator and boost control solenoid for cracks or disconnection. Check whether the wastegate arm moves freely with the engine off. Avoid hard acceleration until it is fixed.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace boost control (wastegate) solenoid | $206-$241 | When the solenoid does not control the wastegate properly. |
| Replace boost pressure sensor | $236-$273 | If the sensor reports boost that does not match a gauge. |
| Replace turbocharger | $2,631-$3,261 | If the wastegate is seized inside the turbo and cannot be freed. |
| Check engine light diagnosis at a shop | $125-$183 | Checks boost control lines and actuator movement before parts. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
Related repair guides
- Kia Sorento Engine Recall: Which Years Get the KSDS Update and the 15-Year/150,000-Mile Warranty
- 2017-2018 Honda CR-V Oil Level Rising or Smells Like Gas? The 1.5T Oil Dilution Problem Explained
- 2010-2013 Chevy Equinox Burning Oil? Fix the 2.4L Engine or Sell It
- 2007-2009 Toyota Camry Burning Oil? What's Going On and What a Fix Costs Now
Related codes
- P0299 Turbocharger/Supercharger "A" Underboost Condition
- P0325 Knock Sensor 1 Circuit (Bank 1 or Single Sensor)
- P0106 Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance
- P0101 Mass or Volume Air Flow "A" Circuit Range/Performance
- P0300 Random/Multiple Cylinder Misfire Detected