Network, generic

U04B5 Invalid Data Received From Brake System Control Module B

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Brake system control module B is a second brake controller. Bosch, for instance, adds a second, redundant brake unit to its Integrated Power Brake on automated vehicles so the car can still be stopped if the main unit fails, and the iBooster plus ESP pairing serves the same purpose. U04B5 is stored when a receiver gets messages from module B that fail plausibility, for example a wrong counter, checksum or pressure value. U0418 is the matching code for the primary brake module, U01B4 marks lost contact with module B and U031C a software mismatch. No manufacturer documents U04B5 publicly. As a safety system it rarely lights the MIL; expect brake or stability warnings, and driver assistance or automated functions may be switched off.

Likely causes

Brake control module B internally faulty
Chassis or private brake bus wiring or connector fault
Software of the two brake modules not matching after update or replacement
Weak supply on the redundant power path

Symptoms

  • Brake, ABS or stability control warning
  • Driver assistance or automated driving functions unavailable

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–2,500
Time0.5–3 h

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

Parts involved

brake system module b

Related codes

U01B4U031CU0418

References: bosch-mobility.com, bosch-mobility.com, en.wikipedia.org.