P259B code meaning
Turbocharger Boost Control Position Sensor B Performance - Stuck High
Powertrain system Generic code P25xx codes Check engine light
What P259B means
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.
P259B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P259B
- Engine warning lamp on
- Power cut-out under full load to prevent overboost
Common causes of P259B
- Most 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)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Turbo actuator position sensor bTurbo actuator b
What each part of P259B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 9B | The exact fault in that area. |
What to do next
- Note P259B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P259B
What does P259B mean?
P259B means "Turbocharger Boost Control Position Sensor B Performance - Stuck High". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P259B?
Drive gently and only to a workshop. With P259B the car can go into limp mode (reduced power) to protect itself.
Will P259B fail an emissions test?
Yes, it can. P259B is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P259B to fix?
Difficulty: hard. A typical repair takes 0.5 to 6 hours of work. This is a job for a workshop.
Will P259B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.