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P04A4 Powertrain

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.

Affected components

  • Exhaust pressure valve b

Common causes

  • High likelihood: Valve stuck open due to soot or broken linkage
  • Low likelihood: Carbon or debris buildup preventing free movement
  • Low likelihood: Component wear with age - mechanical play

Diagnostic notes

  • The malfunction indicator lamp may illuminate
  • This code can affect emissions

Related codes

Sources

Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.

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