Powertrain, generic · Auxiliary emission controls

P049F Exhaust Pressure Control Valve B

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

An exhaust pressure control valve is an electrically driven flap in the exhaust with a position sensor or end-position switch, usually inside the actuator. Valve B is the second such flap; Bentley's V8 assigns A to bank 1 and B to bank 2. Documented uses are the flap behind the particulate filter of VW's and Audi's 2.0 TDI, which raises back pressure for the low-pressure EGR, and the sound flaps of Audi and Bentley. P049F is the general electrical fault of valve B. Audi uses it for sound flap 2 (2017–21, mostly sporadic, with P0475/P0477); on Bentley's Bentayga a commutator short in the flap motor caused by sludge triggers it – if the flap moves freely by hand, the actuator is replaced, otherwise the silencer or pipe.

Likely causes

Flap actuator faulty (commutator short)
Wire or connector at the actuator damaged
Control wire open
Driver in the engine module

Symptoms

  • Check engine light on
  • Flap without function, exhaust sound changed
  • VW/Audi TDI: EGR fault P0401 possible

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€200–1,000
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

exhaust pressure control valve bvalve actuatoractuator wiringengine control module

Related codes

P0475P04A0P04A1P04A2P04A3P04A6

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.