Code
P0242
LAND ROVER
P — Powertrain
Turbocharger/Supercharger Boost Sensor - Circuit B High
Views:
UK: 5
EN: 9
RU: 8
AI status
Completed
Completed
100%
Causes
- Short to battery voltage or 5V reference on boost sensor circuit B
- Failed/defective boost pressure sensor (sensor B)
- Damaged, corroded or bent connector/pins at sensor or PCM
- Poor or open ground for the sensor circuit
- Faulty boost control (wastegate/actuator stuck closed) causing real overboost
- Faulty boost control solenoid or vacuum/pressure lines
Symptoms
- Malfunction Indicator Lamp (MIL)/Check Engine Light illuminated
- Reduced engine power, limp mode or derate
- Poor drivability under boost (surging, hesitation)
- Higher-than-normal boost pressure or overboost events (if mechanical)
- Possible intermittent faults if wiring is damaged
What to check
- Read freeze frame and live data: monitor boost sensor B voltage and compare with boost sensor A, MAP sensor and actual boost pressure.
- Perform a visual inspection of the boost sensor B connector, pins and wiring for damage, corrosion, chafing or repairs.
- Back-probe sensor B signal, reference and ground with key ON and engine OFF; verify reference ~5 V and ground continuity.
- Disconnect sensor B and observe ECM live data: note default or fallback values and whether the fault code changes.
- Wiggle test wiring while monitoring live data to reveal intermittent shorts or opens.
- Inspect boost control components (wastegate actuator, solenoid, vacuum/pressure hoses) for mechanical faults if actual overboost suspected.
Signal parameters
- Sensor reference voltage: typically ~5.0 V (check vehicle specification).
- Expected sensor output range: typically ~0.5–4.5 V proportional to intake/charge pressure (vehicle-specific mapping).
- Circuit high fault threshold: signal at or near supply voltage or > ~4.8–4.9 V (varies by vehicle).
- Circuit low threshold: signal near 0–0.2 V indicates low/short to ground fault.
- Compare sensor B to sensor A or MAP — readings should track closely under similar conditions.
Diagnostic algorithm
- Retrieve and record freeze frame data, all related codes and live data for boost sensors A and B and MAP.
- Visually inspect sensor B connector and wiring harness for damage, corrosion, pin pushed out, or recent repairs.
- With key ON (engine OFF), back-probe: verify 5V reference present at sensor reference terminal, sensor ground continuity to chassis/ECM ground, and measure signal voltage at sensor output.
- If the signal is high at the sensor connector, disconnect the sensor and re-measure signal at the connector. If the voltage remains high with sensor disconnected, suspect wiring short to supply or ECM. If it drops to expected level, suspect sensor failure.
- If wiring appears OK, swap (or temporarily substitute) with a known-good boost/MAP sensor of same type (if available) and re-test to confirm sensor vs harness/ECM.
- Check for a real overboost condition by commanding boost control solenoid or inducing boost while watching live data and inspecting wastegate actuator and hoses for binding or blockage.
- Repair any damaged wiring, replace the sensor if proven faulty, and repair/replace boost control components if mechanical overboost is confirmed.
- If wiring repairs and sensor replacement do not clear the fault and signal remains high, test/replace the PCM as a last resort (after verifying wiring and connectors).
- Clear codes and perform a road test with live-data monitoring to confirm repair and that the code does not return.
Likely causes
- Wiring short to constant battery or reference voltage on sensor B signal wire
- Defective boost pressure sensor (internal short or electronics failure)
- Connector pin corrosion or bent pin at sensor or PCM producing a high voltage reading
- Boost control hardware stuck closed (mechanical overboost) producing legitimately high pressure reading
- Poor sensor ground or high resistance in ground circuit
Fault status
Status
Turbocharger/Supercharger Boost Sensor Circuit B - High input voltage detected. Possible short to supply, sensor failure, faulty ground or real overboost.
Repair difficulty: Medium
Diagnostic time: 1.0 - 2.5 hours
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