P25B3
Turbocharger/Supercharger Wastegate A Stuck Open
Wastegate A is mechanically stuck open. Exhaust gas bypasses the turbine even at low load — turbo cannot reach target speed, boost is permanently low and the engine feels asthmatic. Common causes are seized linkage, broken return spring or carbon-locked wastegate flap.
- 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
- Broken return springPossible
- Carbon or debris buildup preventing free movementLess likely
Parts involved
- Wastegate A
- Turbocharger A
P25B3 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.