What it means
The boost pressure sensor B circuit signal is above the calibrated threshold. This can result from a circuit fault or a failed sensor.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Boost pressure sensor B measures pressure in the turbocharger or supercharger air path and sends a signal to the control module. P0242 sets when the signal rises above the calibrated threshold, which may result from an open signal circuit, a short to battery, or a sensor fault.
Common causes
Most likely first.
- Signal wire open
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Significant power loss / limp mode
- Possible blue or black smoke from exhaust
- Whistling or hissing sound from intake
How to diagnose it
- Review freeze-frame data and boost sensor B live data to see whether the signal went high continuously or intermittently.
- Inspect boost sensor B's connector and harness for an open signal wire, corrosion, pushed-back pins, or a wire pinched against a B+ source.
- Check the sensor mounting and pressure port for looseness, damage, or blockage that could affect the reading.
- Following the manufacturer's circuit procedure, test the signal wire for an open and for a short to battery, and verify terminal contact.
- If the circuit checks out, test boost sensor B against the manufacturer's specifications before replacing it.
Common fixes
- Repair an open signal wire or a wire shorted to battery.
- Repair a pinched or chafed harness and secure it away from power sources.
- Clean or replace corroded or damaged connector terminals.
- Replace boost sensor B if it produces an abnormally high signal with a verified circuit.
Can I keep driving?
With reduced power or limp mode, avoid hard acceleration, towing, and high-speed driving because boost control may be limited. Stop if the vehicle cannot keep up safely with traffic or develops heavy smoke.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.