P25A0: Turbocharger B Boost Control Position At Low Limit

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.

Medium severity. Can I keep driving?Drive without demanding power and go to a repair shop soon. If you see a lot of blue smoke or hear a metallic noise, shut off the engine.

Symptoms

Engine warning lamp on
Lower power than usual, uneven pull

Most 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

What to check, in order

Start with the simplest. You can tick off each step.

Check the hoses, clamps, and intercooler
With the connector unplugged, check whether the signal wire is making contact with ground.
Compare commanded and actual pressure in live data
Check the actuator's movement
Check the vacuum hoses and the solenoid valve
Check the oil and the turbo shaft play before replacing it

Good to know

Repair difficulty: medium
It can trigger limp mode.
It affects emissions.

What each character of P25A0 means

P: Powertrain: engine and transmission
2: Generic code: same on every make
5: Speed and idle
A0: Specific fault in that system

Frequently asked questions

Can I keep driving with code P25A0?

Drive without demanding power and go to a repair shop soon. If you see a lot of blue smoke or hear a metallic noise, shut off the engine.

What causes code P25A0?

The most common causes are: 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.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.