P0238 means Turbocharger/Supercharger Boost Sensor A Circuit High. The boost sensor signal voltage is higher than possible, usually a short to voltage or an open ground. 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 P0238 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.
P0238 symptoms
- Reduced-power mode
- Erratic boost
Common causes of P0238
- Open ground circuit
- Short to voltage
- Failed sensor
How to diagnose P0238
- Check the sensor ground
- Check for shorts to voltage
- Replace the sensor if wiring tests good
Can you drive with P0238?
Gently; repair soon.
P0238 tips
A high-circuit code is usually an open ground or a connector that is not fully latched; check those before buying a sensor. Back-probe the connector with the key on: you should see about 5 volts on the reference, a good ground, and a signal near the barometric value with the engine off. A signal stuck near the reference voltage points to an open ground or a short to voltage.
Will P0238 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 P0238 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 |
|---|---|
| P0236 | Turbocharger/Supercharger Boost Sensor A Circuit Range/Performance |
| P0237 | Turbocharger/Supercharger Boost Sensor A Circuit Low |
| P0234 | Turbocharger/Supercharger A Overboost Condition |
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.
Shipping is a flat $80.00 per order to US addresses, with 15-day free returns. Questions? Ask a parts specialist.