Powertrain, generic (extended)

P25B4 Turbocharger/Supercharger Wastegate A Stuck Closed

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P25B4 is the reverse of P25B3: the module asked wastegate A to open, yet the valve stays shut or opens far too little. Ford uses the same position comparison for both directions (error over 20 mm for 2.5 s); in 2024 it appears as P0243 with failure type 73. Other makers infer the fault from pressure. Porsche explains that its DME judges the wastegate by the boost building up ahead of the throttle; on the 2021 Cayenne E3 PHEV during catalyst warm-up (bulletin 2230) and on Cayenne E-Hybrid models after a dynamic engine start from electric driving (250/22), a weak build-up was misread as a jammed valve, cured by DME software. Audi did the same for the 2018–2019 RS 5. Ford SSM 50670 for 2.3 L EcoBoost Ranger, Bronco and Explorer built from 14 Dec 2021 says: clear, road test under load, and replace the turbo if P25B4 returns.

Likely causes

Wastegate flap or spindle seized shut by carbon or corrosion
Actuator or linkage unable to move the valve
False detection by engine software (Porsche Cayenne, Audi RS 5)
Internal turbocharger fault requiring replacement (Ford SSM 50670)

Symptoms

  • Power reduced because the module limits boost
  • Possible overboost code alongside
  • Check engine lamp on

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–3,500
Time0.5–8 h

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

Parts involved

wastegate aturbocharger a

Related codes

P25B3P25B6P0243P0234P2AB8P2AB9

References: fordservicecontent.com, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.