Network, generic

U02B4 Lost Communication With Front Radar Module A

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

At the front, radar modules measure range and speed of the traffic ahead, which adaptive cruise and automatic braking rely on; corner units also watch crossing traffic. U02B4 means module A no longer answers the assistance controller. No manufacturer documents U02B4 publicly, and letters differ by brand: on the 2026 Mercedes-Benz CLA electric (series 174) the invalid-data partner U05B555 shows that front radar A is the outer left unit, read by controller N62/5. GM uses its own code instead: its 2025 tables report a silent long-range radar as U0235 after 0.25 s, classed as emission-neutral Special Type C without lamp, and switch off adaptive cruise. U02B4 should behave alike: assistance messages, no MIL, normal engine operation. After a bumper repair or radar swap, calibration is often required.

Likely causes

Radar connector behind the bumper not latched, corroded or damaged after a collision
Supply, ground or fuse of the radar interrupted
Radar module failed
Low battery voltage at start-up

Symptoms

  • Adaptive cruise and collision warning unavailable
  • Driver assistance message in the cluster

Repair estimate

DifficultyHardWorkshop job
Parts and labour€50–1,800
Time0.3–3 h

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

Parts involved

front radar module avehicle bus wiring

Related codes

U02B5U05B5U0235

References: static.nhtsa.gov, gsi.ext.gm.com, bosch-mobility.com.