P04A5
Exhaust Pressure Control Valve B Stuck Closed
Same as P04A4 but the valve B is stuck closed - back-pressure stays high even when the engine should run with low restriction; risk of overheating or excessive fuel consumption.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Valve stuck closed due to soot or broken linkageCommon
- Carbon or debris buildup preventing free movementLess likely
- Component wear with age - mechanical playLess likely
Parts involved
- Exhaust Pressure Valve B
P04A5 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.