P0242

Code

Generic P — Powertrain

Turbocharger/Supercharger Boost Sensor B Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 35 EN: 55 RU: 49

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Page language: EN

Causes

Short to voltage on the boost sensor B signal wire (5V or battery voltage)
Failed/shorted boost pressure sensor B
Poor or corroded connector or pin(s)
Open or damaged ground or reference wire causing incorrect reference behavior
PCM internal fault (rare)
Intermittent wiring damage (chafing, broken conductor, water intrusion)

Symptoms

MIL (Check Engine) illuminated
Reduced engine power or limp-in mode depending on vehicle strategy
Incorrect boost gauge/sensor reading in scan tool (very high or pegged)
Poor drivability under boost (hesitation or reduced acceleration)
Reduced fuel economy

What to check

Retrieve freeze frame and live data for boost sensor B and compare to sensor A (if present)
Check for related codes (MAP, boost sensor A/C, turbo control) before repairs
Visually inspect sensor, connector, and harness for damage, corrosion, or oil/water intrusion
Wiggle test harness and connectors while monitoring live data or watch for code reappearance
Measure reference (usually +5 V) and ground at the sensor connector with key ON
Measure sensor signal voltage with key ON and engine running; note if voltage is above ~4.8 V

Signal parameters

Typical sensor circuit: 3-wire sensor — 5 V reference, signal (0.5–4.5 V typical), sensor ground
Circuit-high threshold often >4.8 V (varies by manufacturer)
At engine idle/atmospheric pressure the signal commonly ~0.5–1.5 V; under boost it rises toward ~4.5 V
If sensor disconnected many ECUs will read a high signal (due to internal pull-up) — consult vehicle-specific data

Diagnostic algorithm

Record freeze frame and live data; confirm symptom and that the code is current.
Visually inspect sensor, connector, and harness for damage, oil or water ingress, corrosion, or loose pins.
With key ON (engine OFF) measure reference voltage at the sensor connector (expect ~5 V) and check ground continuity to chassis ground.
Backprobe the signal wire with key ON and engine running; note signal voltage. Compare to expected values and to boost sensor A if present.
If signal is high (>4.8 V), disconnect the sensor and observe signal at the harness. If the harness signal remains high, suspect short to 5 V or PCM pull-up; if it falls or is open, suspect sensor failure.
Check for short to battery/ignition voltage on the signal wire (ohm or voltage test to 12 V with ignition ON). Repair any short or damaged wiring.
Repair or replace corroded connectors, damaged wiring, or the sensor as indicated. Use dielectric grease on connectors after repair where appropriate.
If wiring and sensor test good and the fault remains, consider PCM diagnosis/repair — consult vehicle-specific service information before replacing the PCM.
Clear codes and test drive to confirm the repair; monitor live data for stable, plausible boost readings.

Likely causes

Contaminated/corroded connector at the boost sensor
Shorted signal wire to 5V supply or battery voltage
Failed boost pressure sensor producing out-of-range voltage
Harness damage near turbo/intake or where the harness flexes
Faulty PCM or internal pull-up circuit (least likely)

Fault status

⚠️ Status

PCM has detected the Turbocharger/Supercharger Boost Sensor B signal voltage is higher than the expected maximum range (circuit high). Possible causes include short to voltage, sensor failure, connector/harness fault, or PCM issue.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours