OBD-II code · Powertrain (generic)
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.
Is it safe to drive with P04A4?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyValve stuck open due to soot or broken linkage
- Less likelyCarbon or debris buildup preventing free movement
- Less likelyComponent wear with age - mechanical play
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1.5–4 h
- Emissions test
- Likely to fail
- Parts involved
- Exhaust Pressure Valve B
Related codes
- P047FExhaust Pressure Control Valve A Stuck Open
- P04A1Exhaust Pressure Control Valve B Low
- P04A2Exhaust Pressure Control Valve B High
- P04A3Exhaust Pressure Control Valve B Intermittent
- P04A5Exhaust Pressure Control Valve B Stuck Closed
- P04A6Exhaust Pressure Control Valve B Position Sensor Circuit
- P04A7Exhaust Pressure Control Valve B Position Sensor Circuit Range or Performance
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.