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U05B9 Invalid Data Received From Rear Radar Module C

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

A third rear radar is only needed on vehicles whose rear coverage goes beyond the usual pair of corner sensors, for example to watch longer flanks or the area directly behind. No manufacturer publishes U05B9 or the position of a rear radar C, and its lost-communication partner U02B8 has no public bulletin either. Where letters are documented, they belong to the outer units: Mercedes-Benz uses rear modules A and B for the outer left and right sensors of the 2026 CLA electric and reports them, when unconfigured, with fault type 55. U05B9 would follow the same logic for a further sensor: frames arrive, the content is refused. Configuration, calibration after bumper work and the connector are the first checks. Blind spot or rear crossing alerts may be partly unavailable.

Likely causes

Rear radar C not configured or calibrated after replacement
Sensor position or cover changed by rear body repair
Wiring or connector fault at rear radar C

Symptoms

  • Rear assistance warnings partly unavailable
  • Service message for driver assistance

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,500
Time0.5–3 h

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

Parts involved

rear radar module c

Related codes

U02B8U05BAU05B7

References: bosch-mobility.com, static.nhtsa.gov.