Network, generic

U02B3 Lost Communication With Driver Monitoring System Module

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

The driver monitoring module evaluates an interior camera that follows where the driver looks, how open the eyes are and how the body is held, to judge distraction and drowsiness; the EU's General Safety Regulation makes distraction warning mandatory on all new vehicles from July 2026. U02B3 is logged when this module stops talking to the network. No manufacturer documents U02B3 publicly. Subaru runs a separate DMS control unit on the 2019-2020 Forester and 2020 Legacy and Outback that also stores up to five driver profiles, which technicians back up with SSM4 before service (bulletin 07-175-20). Stellantis names a DMSM among the ADAS modules of the 2022-2025 Grand Cherokee and asks for 90 % battery charge and a 10-minute bus sleep after a deep discharge. Attention warnings and hands-off functions are then lost.

Likely causes

Deep battery discharge or replacement left the module offline
Connector at the camera or module loose, e.g. after steering column or dash work
Driver monitoring module or camera failed

Symptoms

  • Driver attention or drowsiness warning unavailable
  • Hands-free or lane assistance switched off with a service message
  • Stored driver profiles not recognised

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–1,200
Time0.3–2 h

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

Parts involved

driver monitoring modulevehicle bus wiring

Related codes

U05B4

References: static.nhtsa.gov, static.nhtsa.gov, bosch-mobility.com, en.wikipedia.org.