DTC B109E-29: Communication Error Between Body Control Module (BCM) And LF Control Unit [(BCM)]: Outline

WARNING: This page is about a different car, the 2021 Mazda 3. However, it is still accessible from the selected car via links, so may be relevant.

DTC B109E:29 (BODY CONTROL MODULE) DETECTION CONDITION AND POSSIBLE CAUSE

System malfunction location	Communication error between body control module (BCM) and LF control unit
Detection condition	The body control module (BCM) detects the communication error with the LF control unit.
Fail-safe	Not applicable
Possible cause	LF control unit connector or terminal malfunction Body control module (BCM) connector or terminal malfunction Short to ground in LF control unit signal circuit Open circuit in LF control unit signal circuit LF control unit malfunction Body control module (BCM) malfunction
Courtesy of MAZDA MOTORS CORP.