Powertrain
generic / SAE
P04A4
Exhaust Pressure Control Valve B Stuck Open
The exhaust pressure control valve B is mechanically stuck in the open position. The ECU commands closing for back-pressure assist or exhaust braking, but the position feedback shows it remains open - typically heavy soot, broken linkage, or a sticky valve shaft.
SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number4 / A4
Possible causes
- Valve stuck open due to soot or broken linkage high
- Carbon or debris buildup preventing free movement low
- Component wear with age - mechanical play low
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 250–1200 €
- Estimated time: 1.5–4 h
- Component: exhaust pressure valve b
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012