P259BTurbocharger Boost Control Position Sensor B Performance - Stuck High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P259B is logged when the boost control actuator watched by position sensor B is found stuck at the high end of its travel, or fails to return to its rest position, while the sensor signal itself is plausible. A sensor B exists mainly on twin-turbo or two-stage engines. No manufacturer publishes P259B. On the A side, GM checks that the vanes spring back to fully open after the actuator is released and sets P2599 if they stay above 15 % (vacuum) or 5 % (electric); a comparable test for B is likely but not documented. GM bulletin PI1260 shows how vacuum leaks upset such pneumatic actuators. CARB 13 CCR 1968.2 asks for boost control faults to be caught in both directions, including boost above the commanded level. P259A is the low-side partner. The engine may cut power to avoid overboost.
- What you may notice
- Engine warning lamp on
- Power cut-out under full load to prevent overboost
- Likely causes
- LikelyMechanism of charger B seized toward the closed or high position
- PossibleReturn spring or linkage of actuator B binding
- PossibleVacuum solenoid or hose of actuator B faulty (pneumatic systems)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.