What Does P0239 Mean?
The turbocharger boost pressure sensor B circuit has a general malfunction. This is the secondary boost sensor, typically found on twin-turbo vehicles or systems with separate manifold pressure monitoring for each bank. The ECM cannot get reliable boost data from this sensor, compromising boost control for the affected bank. The driver may notice reduced power or asymmetric performance.
Common Causes
35%
Failed boost pressure sensor B providing no or erratic signal
25%
Wiring fault in the boost sensor B circuit (open, short, or high resistance)
20%
Corroded or damaged sensor B connector
12%
Blocked or leaking pressure reference hose to sensor B
8%
ECM 5V reference circuit issue affecting sensor B supply
Diagnostic Steps
1
Read the boost pressure sensor B PID at key-on engine-off — it should match atmospheric pressure (~14.7 psi at sea level). Compare to sensor A — they should read identically at rest.
2
Verify the 5V reference voltage at the sensor B connector with the sensor unplugged (4.9–5.1V expected). Also verify a solid ground connection.
3
Inspect the pressure reference line to sensor B for blockage, cracks, or oil/moisture contamination. Compare the hose condition to the sensor A reference line.
4
Measure sensor B output voltage at idle and under boost and compare to the manufacturer's voltage-to-pressure specification chart. An out-of-spec reading confirms sensor failure.
5
Check the wiring harness from sensor B to the ECM for damage, especially where it routes near the turbo or exhaust system on bank 2.
Estimated Repair Cost
$80 - $400
Parts + labor, varies by vehicle and location
The turbocharger boost pressure sensor B circuit has a general malfunction. This is the secondary boost sensor, typically found on twin-turbo vehicles or systems with separate manifold pressure monitoring for each bank. The ECM cannot get reliable boost data from this sensor, compromising boost cont...
The most common cause of P0239 (Turbocharger Boost Sensor B Circuit Malfunction) is: Failed boost pressure sensor B providing no or erratic signal
Typical repair costs for P0239 range from $80 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Drive gently and avoid heavy boost. Without sensor B data, the ECM may not properly regulate boost on one bank of a twin-turbo system, risking imbalanced boost or undetected overboost. Most ECMs will enter a protective reduced-power mode. Repair before spirited driving or towing.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0239 to identify the root cause.
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Quick Info
Category
Powertrain
System
Turbocharger / Supercharger System
Difficulty
Type
Generic (SAE)
Recommended Tools
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