P0238
UniversalTurbocharger Boost Sensor A Circuit High
High SeverityThe P0238 code indicates that the vehicle's engine control module (ECM) has detected a higher-than-expected voltage signal from the turbocharger/supercharger boost sensor 'A' circuit. This usually means the sensor is reporting abnormally high boost pressure, which can lead to reduced engine power and potential damage if not addressed.
⚠️ Before You Begin (Safety First)
Always ensure the engine is off and cool before working on any components. Disconnect the battery's negative terminal to prevent accidental electrical shorts. Wear appropriate personal protective equipment, such as gloves and eye protection. Be cautious when handling hot engine components.
Common Symptoms
- Check Engine Light illumination
- Reduced engine power or "limp mode"
- Rough idling
- Engine hesitation or stumbling during acceleration
- Black smoke from the exhaust
- Abnormal engine noises (whining, hissing)
Common Causes
- Faulty turbocharger/supercharger boost sensor 'A'
- Open or short in the boost sensor's wiring harness
- Corroded or loose electrical connections at the sensor or ECM
- Faulty ECM (less common)
- Turbocharger wastegate malfunction
Frequently reported on: Ford F-150 EcoBoost (2011-2016), Subaru WRX/STI (2008-2014), Audi A4/A5 (2009-2015), Chevrolet Cruze (2011-2016), BMW 3-Series (N54/N55 engines)
Diagnostic Steps
- Visually inspect the boost sensor 'A' and its wiring harness for any signs of damage, fraying, or loose connections.
- Check for any obvious vacuum leaks around the intake manifold and turbocharger system.
- Clean the electrical connector for the boost sensor with electrical contact cleaner.
- Using a multimeter, test the voltage at the boost sensor connector according to your vehicle's service manual specifications.
- If wiring and connections appear good, consider replacing the turbocharger/supercharger boost sensor 'A'.
- Clear the DTCs and test drive the vehicle to see if the code returns.
👨🔧 When to Call a Professional
If after basic diagnostics and sensor replacement the code persists, or if you notice significant performance issues like severe lack of power or unusual engine noises, it's critical to seek professional diagnostic help immediately to prevent further engine damage.
Commonly Asked Questions
What does "Circuit High" mean for P0238?
"Circuit High" indicates that the ECM is receiving a voltage signal from the boost sensor that is higher than the expected range, suggesting a potential short to voltage or a faulty sensor sending an incorrect high reading.
Can I drive my car with a P0238 code?
It is not recommended to drive extensively with a P0238 code, as it could indicate an issue with boost pressure regulation or sensing, potentially leading to reduced engine performance or even damage if the engine is over-boosting.
How much does it cost to fix P0238?
The cost can vary. A replacement boost sensor typically costs $50-$200 for the part, plus 1-2 hours of labor ($75-$150 per hour) if done by a professional. If the issue is wiring or a more complex turbo problem, costs will be higher.
Is the boost sensor the same as the MAP sensor?
While related, they are distinct. The Boost Sensor specifically measures boost pressure produced by the turbocharger or supercharger, often integrated into a MAP (Manifold Absolute Pressure) sensor, or sometimes a separate sensor in the charge pipe. For P0238, it refers to the sensor responsible for boost measurement.
What tools do I need to diagnose P0238?
You will need an OBD-II scan tool to read and clear codes, a multimeter for electrical testing, and basic hand tools (sockets, wrenches) for accessing and replacing the sensor.