Powertrain, generic (extended)

P259F Turbocharger A Boost Control Position At High Limit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P259F is the counterpart of P259E: the regulation of turbocharger A has hit its upper limit, and measured boost runs above the value the engine computer asked for. In Ford's 2023 diesel OBD summary it is the overboost monitor, checked continuously between 800 (6.7 L) or 1300 rpm (3.0 L) and 4000 rpm with at least 50 or 135 Nm of torque; it sets when actual boost exceeds the target by more than 120 kPa on the 6.7 L or 80 kPa on the 3.0 L for about 10-11 s. Ford bulletin 21-2074 for 2018-2019 Super Duty 6.7 L lists P259F among codes fixed by reprogramming the PCM, so software can be the trigger. More often a vane mechanism stuck toward closed or a wrong boost reading is to blame. P0234 is the separate absolute overboost code.

Likely causes

Vanes or wastegate stuck toward the closed position
Actuator or its vacuum/electrical control not opening as commanded
Engine control software needing an update
Boost pressure sensor reading too high

Symptoms

  • Engine warning lamp on
  • Sudden power cut at high load

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–2,000
Time0.5–5 h

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

Parts involved

turbo actuator awastegate

Related codes

P259EP25A1P0234P2599

References: fordservicecontent.com, static.nhtsa.gov, law.cornell.edu.