P0234 means Turbocharger/Supercharger A Overboost Condition. Boost pressure is higher than the computer allows, so it may cut power to protect the engine. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0234 means
Modern engines measure boost and fuel rail pressure and compare them with a desired value calculated from engine speed, load and throttle. When actual pressure falls short of desired for long enough, the computer sets a code and often reduces power to protect the engine. Watching desired and actual values side by side on a scan tool shows whether the shortfall is constant or only appears under load.
P0234 symptoms
- Sudden loss of power under load
- Reduced-power mode
- Surging
Common causes of P0234
- Wastegate stuck closed or its control solenoid faulty
- Sticking vanes on a variable geometry turbo
- Faulty boost pressure sensor
- Boost control hose problems
How to diagnose P0234
- Compare desired and actual boost on a scan tool
- Check wastegate or VGT actuator movement
- Inspect the boost control hoses and solenoid
- Test the boost sensor
Can you drive with P0234?
Gently only; overboost can damage the engine and turbo.
P0234 tips
Overboost on a turbo gasoline engine usually means the wastegate is not opening, from a sticking wastegate, a faulty control solenoid or a split control hose. On diesels with variable geometry turbos, soot-stuck vanes are a common cause.
Will P0234 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0234 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0299 | Turbocharger/Supercharger A Underboost Condition |
| P2563 | Turbocharger Boost Control Position Sensor A Circuit Range/Performance |
| P0046 | Turbocharger/Supercharger Boost Control A Circuit Range/Performance |
Guides that help
When it is more than a sensor
Our superchargers page lists supercharger kits, and diesel owners can read the 6.7 Cummins turbo guide. If a failed turbo or fuel pump has damaged the engine, compare engines by code on our engines page.
More guides: what does a wastegate do?.
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