What P0239 means
P means powertrain (engine and transmission). The 0 marks a generic code defined by SAE, so the same number means the same thing across makes. The third character, 2, places it in the fuel and air metering, injector circuits subsystem; the last two digits identify the specific fault.
The boost pressure sensor reports pressure after the turbo or supercharger, usually in the charge pipe or intake manifold. The engine computer uses it to close the loop on boost control.
The letter "B" distinguishes between two or more of the same component on one vehicle. Which physical part is "B" is set by the manufacturer, so confirm it in the service information before replacing anything.
What “Circuit” means here
"Circuit" is the broadest fault type in the standard. The module has found the turbocharger / supercharger boost pressure sensor circuit electrically unusable: the signal is missing, outside its electrical limits, or the module's own self-test of the circuit failed. Some vehicles set this instead of the more specific low/high codes; others set it alongside them. Either way the first suspect is the wiring and connector, then the component, and only then the module.
What you may notice
Symptoms depend on the vehicle and on how the module responds to the fault. Any of these can accompany P0239:
- Loss of power or limp-home mode
- Erratic boost or surging
Where to start diagnosing P0239
- Check the 5 V reference, ground and signal at the sensor.
- With the engine off, the sensor should read close to barometric pressure.
- Inspect the sensor port for oil contamination from the crankcase ventilation system.
Clear the code only after recording freeze frame data: it shows the engine speed, load and temperature at the moment the fault set, which is often the best clue to reproducing it.
Live data to watch
These standard OBD2 values relate to P0239. Support varies by vehicle; a value your car does not report will simply be missing.
| Value | What to look for |
|---|---|
| Intake manifold absolute pressure (PID 0x0B) | Key-on engine-off reading should match barometric pressure. |
| Barometric pressure (PID 0x33) | Comparison point. |
Related codes
Codes from the same turbocharger / supercharger boost pressure sensor family. If several are stored together, the shared part — wiring, a common reference voltage, or the component itself — is the place to start.
| Code | Definition |
|---|---|
| P0235 | Turbocharger/Supercharger Boost Sensor "A" Circuit |
| P0236 | Turbocharger/Supercharger Boost Sensor "A" Circuit Range/Performance |
| P0237 | Turbocharger/Supercharger Boost Sensor "A" Circuit Low |
| P0238 | Turbocharger/Supercharger Boost Sensor "A" Circuit High |
| P0240 | Turbocharger/Supercharger Boost Sensor "B" Circuit Range/Performance |
| P0241 | Turbocharger/Supercharger Boost Sensor "B" Circuit Low |
| P0242 | Turbocharger/Supercharger Boost Sensor "B" Circuit High |
Further reading
Frequently Asked Questions
What does P0239 mean?
P0239 is the generic SAE J2012 code for "Turbocharger/Supercharger Boost Sensor "B" Circuit". In plain terms, it means the engine computer has detected a "circuit" fault on the turbocharger / supercharger boost pressure sensor.
Can I keep driving with P0239?
Usually drivable in reduced-power mode. Avoid hard acceleration until repaired.
What should I check first for P0239?
Check the 5 V reference, ground and signal at the sensor.
Definition source: SAE J2012 / ISO 15031-6 generic DTC definitions. This is the generic meaning that applies across makes; a manufacturer can define a code more narrowly or add its own sub-codes, so confirm against the service information for your vehicle before replacing parts. Written by the OBDAssistant engineering team — see our editorial policy.