Powertrain, generic (extended)

P259A Turbocharger Boost Control Position Sensor B Performance - Stuck Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

Likely causes

Sticking vanes, flap or wastegate on charger B
Weak vacuum or electrical supply to actuator B
Worn actuator B or misadjusted linkage

Symptoms

  • Engine warning lamp on
  • Weak acceleration, notably in the range where charger B works

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–2,500
Time0.5–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

turbo actuator position sensor bturbo actuator b

Related codes

P259BP2598P2587P2586

References: law.cornell.edu, fordservicecontent.com, gsi.ext.gm.com.