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Diagnostic Trouble Code (DTC) U20B400 indicates that the Battery Management System (BMS) has detected a CAN communication timeout involving Battery Information Collector 5 (BIC5). Workshop references for the BYD ATTO 3/Yuan Plus identify U20B400 specifically as the BIC5 CAN Communication Timeout fault.
BIC5 is part of the high-voltage battery monitoring system and communicates battery-monitoring information to the BMS through the battery CAN network. When expected communication from BIC5 is not received within the required time, the BMS can store U20B400.
Loss of communication with BIC5 may prevent the BMS from receiving reliable cell-voltage and battery-temperature information from the section monitored by BIC5. As a protective measure, the BMS may restrict charging, reduce available vehicle power, or disable high-voltage operation.
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BIC5 is part of the high-voltage battery monitoring system and communicates battery-monitoring information to the BMS through the battery CAN network. When expected communication from BIC5 is not received within the required time, the BMS can store U20B400.
Loss of communication with BIC5 may prevent the BMS from receiving reliable cell-voltage and battery-temperature information from the section monitored by BIC5. As a protective measure, the BMS may restrict charging, reduce available vehicle power, or disable high-voltage operation.
BYD ATTO 3 (e-Platform 3.0) U20B400 BIC5 CAN Communication Timeout Fault - New Zealand and Australia Motors
BYD ATTO 3 (e-Platform 3.0) U20B400 BIC5 CAN Communication Timeout Fault symptoms, causes and diagnosis covering BIC5, CAN-H, CAN-L, BMS, wiring, connectors, power supply, communication network, battery monitoring, and high-voltage battery troubleshooting.