Powertrain, generic · Auxiliary emission controls

P04A3 Exhaust Pressure Control Valve B Intermittent

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. P04A3 means an intermittent circuit fault at valve B's actuator. Audi and Bentley store such faults as P049F with an intermittent status instead. No manufacturer document available to us uses this code; the description mirrors the valve A counterpart P0479 and CARB's monitoring requirement for input and output components.

Likely causes

Loose contact or corrosion in the connector
Commutator in the actuator partly shorted
Wire broken by vibration

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€50–800
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

P049FP04A1P04A2P0479

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