Powertrain, generic (extended)

P259C Excessive Time To Enter Closed Loop Turbocharger A Boost Control

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

P259C reports that closed-loop boost control of turbocharger A was not reached within the expected time after its enabling conditions were met. Instead of trimming the actuator from boost or position feedback, the controller stays in open-loop or default mode. CARB 13 CCR 1968.2 requires diesel OBD systems with feedback boost control to report it when control fails to start inside a time window set by the manufacturer, and P259C is the code for that case. No manufacturer publishes thresholds for P259C. Ford's 2023 diesel summary shows why it matters: its underboost check for turbocharger A runs only while boost feedback control is active. Typical root causes are inputs the loop needs, such as a faulty boost or position sensor, or a stored actuator fault. P259D is the turbocharger B equivalent.

Likely causes

Boost pressure or actuator position sensor fault that blocks closed-loop control

Actuator A fault, often with its own stored code

Charge air leak preventing boost from reaching the range where control starts

Engine control software issue

Symptoms

Engine warning lamp on
Sluggish or uneven boost build-up

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€60–1,200

Time0.5–4 h

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

Parts involved

turbo actuator a

Related codes

P259D P2263 P0046 P0236

References: law.cornell.edu, fordservicecontent.com.