Powertrain, generic · Auxiliary emission controls

P04A0 Exhaust Pressure Control Valve B Range/Performance

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. P04A0 is the function check of valve B: it is electrically sound but does not reach its target or full travel. Bentley documents it on the V8 of 2023 for bank 2 (with P04A8) and on the Bentayga (with P049F): the code sets when the actuator does not run through its full range, caused by sludge at the commutator or a stiff flap.

Likely causes

Flap actuator worn, commutator dirty
Flap shaft stiff (corrosion, deposits)
Wiring or contacts
Basic setting not carried out

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€200–1,500
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

P0476P049FP04A4P04A5P04A7P04A8

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