P0242 Turbocharger/Supercharger Boost Sensor B Circuit High

P0242 points to boost sensor B circuit high. The second boost pressure signal is open, shorted to voltage, or reporting implausibly high pressure.

Code details

Generic OBD-II · P0

System: Fuel / Air
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace turbocharger components before isolating the high boost sensor B signal path.

Symptoms of P0242

Check-engine light on, sometimes with rough or uneven running.
Hesitation, surging, or a noticeable change in fuel economy.
Occasionally hard starting or a smell of unburnt fuel.

Common causes of P0242

A failing or contaminated sensor (MAF, MAP, oxygen or air-fuel sensor).
Intake or vacuum leaks, or an exhaust leak near an upstream sensor.
Wiring, connector, or fuel-delivery problems that skew the reading.

Useful checks before replacing parts

Check boost sensor B signal voltage, ground path, open circuits, short-to-voltage faults, connector fit, and reference voltage.
Compare sensor B with sensor A, MAP, BARO, throttle angle, desired boost, and key-on engine-off readings.
Inspect charge-pipe harness routing, water intrusion, connector corrosion, and wiring disturbed during intake or intercooler service.

Related OBD-II codes

These nearby fuel / air entries can help compare wording and pin down the fault area.