Powertrain, generic · Auxiliary emission controls

P048D Exhaust Pressure Control Valve A Position Sensor/Switch Circuit Low

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 A is the first 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. P048D means valve A's position signal is below its permitted voltage window – the signal wire is shorted to ground or the sensor's 5 V supply is missing. Bentley's Continental and Flying Spur V8 of 2023 report it for bank 1 together with P048B; the bulletin advises checking wiring and contacts, otherwise replacing the actuator and carrying out the basic setting.

Likely causes

Signal wire shorted to ground (chafed at the underbody)
Position sensor or actuator faulty internally
5 V sensor supply open or shorted
Moisture or corrosion 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€100–900
Time0.5–2.5 h

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

Parts involved

exhaust pressure control valve a position sensorexhaust pressure control valve asensor wiringengine control module

Related codes

P048BP048EP048CP048FP04A8

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