P0238 is a generic OBD-II trouble code that indicates a high signal from the Turbocharger Boost Sensor A circuit. The ECM/PCM has detected that the sensor signal voltage is higher than the expected range. The cause may be a faulty boost pressure sensor, wiring problem, electrical connection issue, or another fault in the sensor circuit.
What Does P0238 Mean?
P0238 means the engine control module (ECM/PCM) is receiving an abnormally high signal from the Turbocharger Boost Sensor A circuit. The boost sensor measures pressure in the intake or charge-air system and sends a voltage signal to the engine computer.
When the signal is higher than the expected value for the current engine conditions, the ECM/PCM can store P0238 and illuminate the Check Engine Light. Some vehicles may reduce engine power or enter limp mode to protect the engine and turbocharger system.
P0238 Symptoms
- Check Engine Light
- Reduced engine power
- Poor acceleration
- Turbocharger performance problems
- Engine hesitation
- Abnormal or inconsistent boost pressure
- Reduced fuel economy
- Limp mode on some vehicles
Common Causes of P0238
- Faulty Turbocharger Boost Sensor A
- Short to voltage in the sensor signal circuit
- Damaged or incorrectly connected wiring
- Corroded or damaged electrical connector
- Incorrect sensor reference voltage
- Poor sensor ground
- Sensor signal circuit interference
- ECM/PCM fault in rare cases
How to Diagnose P0238
1. Scan for Trouble Codes
Use an OBD-II scanner to confirm P0238 and check for additional codes. Related sensor, reference voltage, or communication codes may provide important diagnostic information.
2. Inspect the Boost Sensor
Locate Turbocharger Boost Sensor A and inspect the sensor and connector for physical damage, corrosion, contamination, loose terminals, or poor connections.
3. Inspect the Wiring
Check the wiring between the boost sensor and ECM/PCM. Pay particular attention to a signal wire that may be shorted to battery voltage or another voltage source.
4. Test the Reference and Ground Circuits
Use a digital multimeter to verify the sensor reference voltage and ground circuit. Many automotive pressure sensors use a 5-volt reference, but the exact circuit design varies by vehicle.
5. Test the Signal Circuit
Measure the boost sensor signal according to the manufacturer's specifications. An abnormally high signal can be caused by a short to voltage, incorrect reference voltage, poor ground, or a defective sensor.
6. Compare Live Data
Monitor boost pressure and related sensor data with a scan tool. Compare the reported pressure with actual engine operating conditions and the manufacturer's specifications.
P0238 Wiring and Signal Flow
Note: Pinouts, wire colors, reference voltages, and signal ranges vary between vehicle makes and models. Always use the wiring diagram and specifications for the specific vehicle.
How to Fix P0238
The correct repair depends on the result of the diagnostic tests. Possible repairs include:
- Repairing a shorted signal wire
- Repairing damaged or corroded connector terminals
- Repairing the sensor ground or reference circuit
- Replacing a faulty boost pressure sensor
- Repairing related wiring problems
- Diagnosing the ECM/PCM if all other components and circuits test correctly
Do not automatically replace the boost sensor when P0238 is stored. A short to voltage in the signal circuit can produce the same code.
P0238 Repair Cost
The repair cost for P0238 depends on the vehicle, labor rates, parts prices, and the actual cause of the high sensor signal.
- Diagnostic testing: approximately $50–$150
- Wiring or connector repair: approximately $50–$300
- Boost pressure sensor replacement: approximately $100–$300
These figures are general estimates and can vary significantly between vehicles and repair shops.
Can I Drive with P0238?
You may be able to drive a short distance if the vehicle runs normally and there is no major loss of power. However, P0238 can affect turbocharger boost control and engine performance.
If the vehicle has severe power loss, enters limp mode, develops unusual turbocharger symptoms, or shows other serious engine problems, it is better to avoid continued driving until the fault is diagnosed.
Common Repair Mistakes
- Replacing the boost sensor without testing the signal circuit
- Failing to check for a short to voltage
- Ignoring the sensor ground circuit
- Assuming the turbocharger itself is defective
- Failing to inspect connector terminals
- Ignoring additional diagnostic trouble codes
Recommended Diagnostic Tools
- OBD-II diagnostic scanner
- Digital multimeter
- Vehicle-specific wiring diagram
- Back-probe test leads
- Electrical circuit tester
FAQ
Can a bad boost sensor cause P0238?
Yes. A faulty boost sensor can cause P0238, but the signal wiring, reference voltage, ground, and connector should also be tested before replacing the sensor.
Is P0238 serious?
P0238 can affect engine performance and turbocharger boost control. The severity depends on the vehicle and the underlying cause.
Can a wiring problem cause P0238?
Yes. A signal wire shorted to voltage or another electrical fault can cause the ECM/PCM to detect an excessively high sensor signal.
Related DTC Codes
- P0235 – Turbocharger Boost Sensor A Circuit Malfunction: A general fault in the Turbocharger Boost Sensor A circuit.
- P0236 – Turbocharger Boost Sensor A Circuit Range/Performance: The boost sensor signal is outside the expected range or does not match operating conditions.
- P0237 – Turbocharger Boost Sensor A Circuit Low: The boost sensor signal is lower than the expected value.
- P0239 – Turbocharger Boost Sensor B Circuit Malfunction: A fault involving the Turbocharger Boost Sensor B circuit.