P259FTurbocharger A Boost Control Position At High Limit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- Engine warning lamp on
- Sudden power cut at high load
- Likely causes
- LikelyVanes or wastegate stuck toward the closed position
- PossibleActuator or its vacuum/electrical control not opening as commanded
- PossibleEngine control software needing an update
- RareBoost pressure sensor reading too high
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.