Powertrain, generic · Auxiliary emission controls

P04A7 Exhaust Pressure Control Valve B Position Sensor/Switch Circuit 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. P04A7 means valve B's position signal is valid but does not fit the commanded position or the learned end stops. No manufacturer document available to us uses this code; the description mirrors the valve A counterpart P048C and CARB's monitoring requirement for input and output components.

Likely causes

Flap or shaft corroded or coked (stiff)
End positions not relearned after replacement
Position sensor in the actuator drifting
Contact resistance in the connector

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€150–1,200
Time0.5–2.5 h

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

Parts involved

exhaust pressure control valve b position sensorexhaust pressure control valve bsensor wiringengine control module

Related codes

P04A6P04A8P04A9P04A0P048C

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