Powertrain, generic (extended)

P259D Excessive Time To Enter Closed Loop Turbocharger B Boost Control

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P259D is the turbocharger B version of the closed-loop timing fault. On engines with two separately regulated chargers, the control unit expects the boost regulation of the second unit to switch to feedback operation within a set time, and here it did not. No manufacturer documents P259D publicly with thresholds; the basis is CARB 13 CCR 1968.2, which asks for a malfunction when feedback boost control does not start in time or falls back to default operation. GM's 2018 diesel table illustrates the dependency on the A side: its actuator plausibility checks only run while VGT position feedback is active and no fault is present on the position sensor or the actuator circuit. A stored sensor or actuator fault on charger B is therefore the first thing to repair. P259C covers turbocharger A.

Likely causes

Fault on position or pressure sensing for charger B
Actuator B or its control circuit faulty
Leak in the charge air path of charger B

Symptoms

  • Engine warning lamp on
  • Reduced power, especially at higher load

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–1,500
Time0.5–5 h

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

Parts involved

turbo actuator b

Related codes

P259CP2587P2586

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