P0239 is a generic OBD-II trouble code that indicates a problem with the Turbocharger/Supercharger Boost Sensor B circuit. The ECM/PCM has detected an abnormal electrical signal from the boost pressure sensor circuit.
What Does P0239 Mean?
P0239 means the Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected an abnormal signal from Boost Sensor B.
The sensor monitors pressure within the turbocharger or supercharger system and sends a voltage signal to the ECM/PCM. If the signal does not match the expected operating conditions, the module may store P0239 and illuminate the Check Engine Light.
The exact sensor location, wiring configuration, and naming of Boost Sensor B can vary between vehicle manufacturers and engine configurations.
Common Causes of P0239
- Faulty Turbocharger/Supercharger Boost Sensor B.
- Open circuit in the boost sensor wiring.
- Short circuit in the boost sensor wiring.
- Incorrect or missing reference voltage.
- Poor sensor ground.
- Corroded, loose, or damaged connector terminals.
- Damaged boost pressure hose or pressure passage.
- Problems with turbocharger or supercharger control components.
- ECM/PCM fault in rare cases.
Symptoms of P0239
- Check Engine Light.
- Reduced engine power.
- Slow acceleration.
- Engine hesitation.
- Unstable boost pressure.
- Turbocharger or supercharger performance problems.
- Limp mode.
- Poor fuel economy.
- Abnormal boost pressure readings on a scan tool.
Can I Drive with P0239?
Driving with P0239 may be possible if the vehicle is operating normally, but continued driving should be avoided if there is major power loss, excessive boost, unusual turbocharger noise, heavy smoke, or limp mode.
An incorrect boost pressure signal can cause the ECM/PCM to control engine boost incorrectly. Avoid heavy acceleration until the cause has been identified.
How to Fix P0239
The correct repair depends on the cause of the code. Possible repairs include:
- Replace a defective Boost Sensor B.
- Repair broken or damaged wiring.
- Repair loose or corroded connector terminals.
- Repair damaged boost pressure hoses or passages.
- Restore the correct sensor reference voltage.
- Repair the sensor ground circuit.
- Repair a short or open signal circuit.
- Repair faults in the turbocharger or supercharger control system.
- Clear the code and perform a road test after completing the repair.
Common Repair Mistakes
- Replacing the boost sensor without testing the circuit.
- Ignoring damaged or corroded connectors.
- Assuming the turbocharger itself is defective.
- Failing to check the reference voltage.
- Failing to verify the sensor ground.
- Ignoring damaged boost hoses.
- Using an incorrect sensor pinout.
- Failing to compare sensor readings with actual boost pressure.
P0239 Repair Cost
The repair cost varies depending on the vehicle, labor rates, and the actual cause of the fault.
A wiring or connector repair may be relatively inexpensive, while replacing a boost pressure sensor or repairing turbocharger control components can cost more.
Proper diagnosis is important because replacing the sensor unnecessarily can increase repair costs without solving the problem.
Technical Information
Where Is the P0239 Fault Located?
The fault is located in the electrical circuit associated with Turbocharger/Supercharger Boost Sensor B.
Depending on the vehicle, the sensor may be installed on or near the intake system, charge-air piping, intake manifold, turbocharger system, or another location specified by the manufacturer.
Because manufacturers use different sensor layouts, the exact physical location should be confirmed using the vehicle-specific service information.
Component Responsible for P0239
The primary component associated with P0239 is Boost Sensor B, but the sensor itself is not always the failed component.
The fault can also involve the sensor signal wire, reference voltage circuit, ground circuit, connector, wiring harness, pressure hose, or the ECM/PCM.
The exact definition and component arrangement can vary by manufacturer. Always verify the manufacturer's wiring diagram and diagnostic procedure for the specific vehicle.
Signal Flow
Reference Voltage
Boost Sensor B
Pressure Measurement
Signal Voltage
ECM / PCM
The ECM/PCM supplies the sensor circuit with the required reference voltage and ground. Boost Sensor B converts pressure changes into a voltage signal, which is returned to the ECM/PCM for engine control calculations.
How to Diagnose P0239
- Connect an OBD-II scanner and confirm P0239.
- Check for additional turbocharger, supercharger, or boost pressure codes.
- Locate Boost Sensor B using the vehicle-specific service information.
- Inspect the sensor and connector for physical damage.
- Check the wiring for broken, melted, corroded, or shorted wires.
- Measure the sensor reference voltage according to manufacturer specifications.
- Test the sensor ground circuit.
- Measure the sensor signal voltage.
- Compare the sensor reading with actual pressure conditions.
- Inspect boost pressure hoses and passages for leaks or restrictions.
- If the sensor circuit is operating correctly, inspect the turbocharger or supercharger control system.
- Repair the identified fault, clear the code, and perform a road test.
Related DTC Codes
Turbocharger/Supercharger Boost Sensor A Circuit
Turbocharger/Supercharger Boost Sensor A Circuit Range/Performance
Turbocharger/Supercharger Boost Sensor A Circuit Low
Turbocharger/Supercharger Boost Sensor A Circuit High
Common Questions About P0239
Does P0239 always mean the boost sensor is bad?
No. The code can be caused by wiring, connectors, reference voltage, ground problems, pressure-related issues, or other faults in the boost sensing system.
Can P0239 cause limp mode?
Yes. Some vehicles may reduce engine power or enter limp mode when the ECM/PCM detects an unreliable boost pressure signal.
Can a boost leak cause P0239?
A boost leak can affect pressure readings and engine performance, although the exact relationship depends on the vehicle's design and diagnostic strategy. The electrical circuit should also be tested.
What should I check first with P0239?
Start with the boost sensor connector and wiring, then verify the reference voltage, ground, and signal circuit before replacing the sensor.