Powertrain, generic (extended)

P25A0 Turbocharger B Boost Control Position At Low Limit

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P25A0 says the regulator of turbocharger B has run to its low limit without reaching the boost target, so the second charger delivers too little pressure even with full control authority. It only exists on engines where two chargers are regulated separately. No manufacturer documents P25A0 publicly. CARB 13 CCR 1968.2 requires a fault once boost feedback control has used all of its adjustment and still misses the target, which describes this case. For the A side, Ford flags the same situation as P259E when requested boost exceeds measured boost by 120 kPa on its 6.7 L diesel for about 10 s. Leaks between charger B and the intake, a sticking wastegate or vanes and sensor errors are the usual suspects. P25A1 is the high-limit partner, P259E the turbocharger A version.

Likely causes

Leak in the charge air path served by charger B
Wastegate or vanes of charger B not closing as commanded
Worn or damaged charger B

Symptoms

  • Engine warning lamp on
  • Lower power than usual, uneven pull

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–2,500
Time0.5–6 h

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

Parts involved

turbo actuator b

Related codes

P25A1P259EP259A

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