P25B5
Turbocharger/Supercharger Wastegate B Stuck Open
Same as wastegate A stuck open, applied to the second wastegate (twin-turbo, sequential or two-stage). Boost control tracks commanded vs. actual manifold pressure; persistent deviation means wastegate, vanes, hose or actuator are not delivering the requested pressure.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Symptoms
- Check engine light on
- Significant power loss / limp mode
- Possible blue or black smoke from exhaust
- Whistling or hissing sound from intake
Common causes
Ordered by how often each turns out to be the cause.
- Seized wastegate linkageCommon
- Carbon or debris buildup preventing free movementLess likely
- Component wear with age - mechanical playLess likely
Parts involved
- Wastegate B
- Turbocharger B
P25B5 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.