OBD-II Code
P0242
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$75–$400
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P0242 is the bank-2 / sensor-B boost-pressure sensor 'circuit low' fault - the signal voltage has dropped below the lower electrical threshold the ECU monitors, typically below 0.25V (well under what a healthy sensor reads even at atmospheric pressure).
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP0242 is the bank-2 / sensor-B boost-pressure sensor 'circuit low' fault - the signal voltage has dropped below the lower electrical threshold the EC…
P0242 is the bank-2 / sensor-B boost-pressure sensor 'circuit low' fault - the signal voltage has dropped below the lower electrical threshold the ECU monitors, typically below 0.25V (well under what a healthy sensor reads even at atmospheric pressure). This is a hard circuit code, not a performance code, which means the fault is electrical: a wiring short to ground, a dead sensor with internal shorted output, or a missing 5V reference.
Diagnostic order on a shop floor
- Disconnect the sensor and read voltage at the signal pin of the connector with KOEO - a healthy 5V reference and a floating signal mean the sensor is the failed component; if the signal pin reads zero with the sensor disconnected, the harness is shorted to ground somewhere between the sensor and the ECU.
- Check the 5V reference at the connector - many boost sensors share a 5V bus with other sensors (MAP, TPS), so a shorted boost sensor can pull the entire 5V bus down and throw multiple codes at once; if you see P0242 plus P0123 or P0108 simultaneously, the boost sensor shorting the bus is the most likely root cause.
- Wiggle-test the harness around any clip points where the wiring routes near hot exhaust or sharp brackets - chafed insulation that shorts to a ground plane is a classic intermittent P0242. The 15-minute DMM check almost always nails the fault to either harness or sensor before any parts are bought.
Vehicle-specific patterns2008-2013 BMW N63 twin-turbo V8 (550i, 750i, X5/X6 5.0i) commonly throws P0242 from a failed boost-pressure sensor on the bank-2 charge pipe - heat-s…
- 2008-2013BMW N63 twin-turbo V8 (550i, 750i, X5/X6 5.0i) commonly throws P0242 from a failed boost-pressure sensor on the bank-2 charge pipe - heat-soak under the V8 cooks the sensor electronics.
- 2011-2016Ford F-150 3.5L EcoBoost throws P0242 from chafed sensor wiring at the intercooler-pipe bracket on the passenger side; Ford TSB coverage exists for harness retainers on early-build trucks.
- 2007-2010BMW 135i / 335i / 535i with the N54 throws P0242 from a connector pin that backs out under vibration - re-seat and dielectric-grease the connector before quoting a sensor.
- 2013-2018Chevy Cruze 1.4L / 1.8L turbo and Sonic 1.4L turbo throw P0242 from a failing post-intercooler MAP sensor (referenced as sensor B in service data) that GM has a known supplier-quality issue with.
Estimated repair$75 to $400
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