Code
P0239
GWM
P — Powertrain
- Malfunction of turbocharger sensor B
Views:
UK: 2
EN: 2
RU: 1
AI status
Completed
Completed
100%
Causes
- Faulty turbocharger boost (MAP) sensor B
- Damaged, corroded or loose connector at sensor B
- Wiring open, short to ground or short to battery in sensor B circuit
- Poor or intermittent sensor ground or reference voltage (5V) loss
- ECM input circuit fault
- Intake system leak or mechanical turbocharger fault causing implausible readings
Symptoms
- MIL / Check Engine Light illuminated
- Reduced engine power, limp-home mode or turbo underboost protection
- Poor throttle response, hesitation or stalling under load
- Erratic boost readings in live data (jumps, stuck values)
- Possible increased fuel consumption or smoke under heavy load
What to check
- Read freeze-frame and stored data with a scan tool; note engine conditions when code set
- Check for related codes (boost, MAP, turbo actuator, MAF) that may help narrow cause
- Visually inspect sensor B, connector and wiring for damage, corrosion, pin push-out or rodent damage
- Back-probe sensor connector with ignition ON and engine running to measure signal, 5V reference and ground
- Verify continuity from sensor connector to ECM for signal, reference and ground (check for shorts to battery or ground)
- Compare sensor B live data to sensor A (if present) and to expected values at idle and under boost
Signal parameters
- Typical sensor type: 3-wire pressure sensor (5V reference, signal, ground)
- Expected signal voltage range: ~0.5 V (vacuum/low boost) to ~4.5 V (high boost) — manufacturer may vary
- At key ON, engine OFF: signal often near vacuum value (approx. 0.5–1.5 V)
- At idle: low positive pressure voltage (approx. 0.7–1.5 V)
- Under full boost: signal approaches upper range (approx. 3.0–4.5 V)
- Open circuit: signal may read ~0 V; short to battery: signal >4.8–5.0 V
Diagnostic algorithm
- Retrieve all stored and pending codes and freeze-frame data. Note conditions (RPM, load, boost) when P0239 set.
- Perform a visual inspection of the intake plumbing, vacuum lines and turbocharger for leaks or mechanical issues that could cause implausible readings.
- Inspect sensor B connector and wiring for damage, pin corrosion, bent pins or water intrusion. Repair or reseat connector as needed.
- With connector connected, back-probe and measure: 5V reference (with ignition ON), sensor ground continuity, and the signal voltage with engine off and running. Compare to expected ranges.
- Check continuity between sensor ground and chassis ground; check continuity of signal wire to ECM pin for opens or shorts. Wiggle wiring while watching live data for intermittent faults.
- If signal is out of range, disconnect sensor and measure signal pin at connector for open/short behavior. If reference or ground missing, trace and repair wiring harness.
- If wiring and reference are good, swap sensor B with sensor A (if identical and practical) or install a known-good sensor to confirm sensor failure.
- If wiring and sensors check OK but fault persists, inspect ECM connector and pin for damage. Consider ECM diagnostics/repair as last resort.
- After repairs, clear codes, perform functional test and road test under conditions that previously set the code. Re-scan for return of code.
- If intermittent, monitor live data and consider using an oscilloscope to capture transient faults during load changes.
Likely causes
- Damaged wiring or connector to boost sensor B (most common)
- Failed boost/MAP sensor B
- Intermittent ground or lost 5V reference to the sensor
Fault status
Status
P0239 — Turbocharger boost sensor B circuit malfunction (signal open, short, or out of range).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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