DTC codes / P25xx · Vehicle speed, idle control and auxiliary inputs / P259B
P259B indicates that the powertrain control module has detected a performance fault in the turbocharger boost control position sensor B circuit, specifically that the sensor signal is stuck at a high voltage or indicates a position that is higher than commanded for an extended period. The computer compares the commanded boost control position with the actual sensor feedback and sets this code when the feedback remains abnormally high, suggesting a short to voltage, a failed sensor, or a mechanical binding in the turbocharger's variable geometry or wastegate mechanism.
Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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