Volvo All Engines (2017 Emissions) Fault Code: P047F71 PID: EMS Exhaust Pressure Control Valve “A” Stuck Open

Volvo All Engines (2017 Emissions) Fault Code: P047F71 PID: EMS Exhaust Pressure Control Valve “A” Stuck Open

Circuit description
The purpose of the engine exhaust brake closed loop butterfly valve (butterfly valve) is to create a controlled exhaust back pressure upstream of the butterfly valve. The butterfly valve consists of the housing, shutter, shaft, bushings, pneumatic actuator, spring, and a bracket assembly. The shutter is kept in an open position by the spring when not activated. A pneumatic actuator closes the shutter when activated. The actuator is activated by the Engine Control Module (ECM). An exhaust pressure sensor located upstream from the shutter monitors the upstream exhaust pressure. The ECM activates the pneumatic actuator and closes the shutter when the upstream exhaust pressure deviates from the requested value. Once the pneumatic actuator is deactivated, the shutter returns to the open position

Conditions for diagnostic trouble code (DTC)
Sensor value does not change with changing conditions

Observable symptoms
Engine brake, poor brake performance/Brake performance too high

Probable cause
1) Exhaust back pressure sensor
2) Leakage from hoses or connections
3) Clogged or blocked air system