P259A code meaning
Turbocharger Boost Control Position Sensor B Performance - Stuck Low
Powertrain system Generic code P25xx codes Check engine light
What P259A means
P259A applies to engines with a second boost control actuator, for instance a twin-turbo layout or the second stage of a two-stage system, whose position is read by sensor B. The code is stored when that actuator's reported position stays at the low end and stops tracking the command even though the signal is electrically sound. No manufacturer documents P259A publicly. Its logic mirrors P2598 on the A side, where Ford compares requested with actual position and reacts to more than 15 % for 25 s, and GM counts samples with vanes more open than requested. CARB 13 CCR 1968.2 requires the boost control system to report faults that stop it from reaching its target. P259B is the high-side counterpart; circuit faults of sensor B fall under P2586-P2590. Reduced power is the usual result.
P259A at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 6 hours
- Clears after repairAfter a drive cycle
Symptoms of P259A
- Engine warning lamp on
- Weak acceleration, notably in the range where charger B works
Common causes of P259A
- Most likelySticking vanes, flap or wastegate on charger B
- PossibleWeak vacuum or electrical supply to actuator B
- PossibleWorn actuator B or misadjusted linkage
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 P259A 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. |
| 9A | The exact fault in that area. |
What to do next
- Note P259A 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 P259A
What does P259A mean?
P259A means "Turbocharger Boost Control Position Sensor B Performance - Stuck Low". P259A applies to engines with a second boost control actuator, for instance a twin-turbo layout or the second stage of a two-stage system, whose position is read by sensor B. It is a generic code, so it means the same on every make.
Is it safe to drive with P259A?
Drive gently and only to a workshop. With P259A the car can go into limp mode (reduced power) to protect itself.
Will P259A fail an emissions test?
Yes, it can. P259A 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 P259A to fix?
Difficulty: hard. A typical repair takes 0.5 to 6 hours of work. This is a job for a workshop.
Will P259A clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.