Turbo/Supercharger Boost Sensor B Circuit High
The P0238 code means the vehicle's onboard diagnostic system has detected: Turbo/Supercharger Boost Sensor B Circuit High. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- moderate
- Estimated cost
- $80 - $350 (parts and labor)
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Common Symptoms
- Check Engine Light on
- Reduced turbo boost
- Engine may cut fuel under boost
- Loss of power with possible misfires
Probable Causes (Ranked by Likelihood)
- Open circuit in boost sensor B signal wire Very High
- Failed boost pressure sensor B (open) High
- Disconnected sensor connector Moderate
- Short to 5V reference wire Low
Step-by-Step Diagnostic Procedure
-
Read boost sensor B voltage. Above 4.8V at key-on engine-off confirms high circuit.
-
Check sensor connector is fully seated.
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Measure signal wire continuity from sensor to PCM.
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Inspect for shorts between signal wire and 5V reference wire in the harness.
Frequently Asked Questions
What does circuit high mean for boost sensor B?
The PCM sees a voltage above the expected maximum, usually from an open circuit (signal wire disconnected) or a short to the 5V reference.
Can a disconnected sensor cause P0238?
Yes, if the connector is not fully seated, the signal line becomes open and floats to a high voltage.
Is P0238 a turbo failure?
No, P0238 is a sensor circuit issue, not a turbo failure. The turbo itself is likely fine; the sensor or wiring needs repair.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0238 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
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