DTC codes / U01xx · Lost communication with a control module / U01B3
U01B3 is a generic communication fault indicating that a control module on the vehicle's network has stopped receiving valid messages from the brake blending actuator, which is the component that coordinates friction braking with regenerative braking on hybrid and electric vehicles. The computer detects this when the expected controller area network (CAN) messages from the actuator either time out or fail their checksum, and it then stores the code and illuminates the brake system warning lamp.
Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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