Network, generic

U04BC Invalid Data Received From Switch Input Module C

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

With a third switch input module, addressing becomes a weak point. Several near-identical switch units often hang on one LIN line as slaves, and each needs its own node address, assigned either by part variant or by an auto-addressing routine at start-up. If two units end up with the same address, or a reply arrives with a bad LIN checksum, the master receives data it cannot assign and the controller records U04BC for module C. Nothing public ties this code to a specific make or to a fixed location in the car. U01B9 covers the case where module C does not answer at all, and U04BD, which follows in the list, belongs to the park lock module rather than to this series. Effects stay limited to the buttons wired to module C.

Likely causes

Two switch units with the same LIN node address after replacement or failed auto-addressing
Switch input module C internally faulty
Interference on the shared LIN line, e.g. damaged insulation

Symptoms

  • Buttons of module C ignored while other switch groups work
  • Button presses assigned to the wrong function

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–350
Time0.5–2.5 h

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

Parts involved

switch input module c

Related codes

U01B9U04BAU04BB

References: en.wikipedia.org, patents.google.com.