In Mitsubishi's electronic management system, every registered key fob is assigned a number. Code B1A10 corresponds to the registered with the KOS-ECU.

Rarely, the KOS-ECU , ETACS-ECU, or WCM may be failing and misinterpreting signals. How to Fix and Clear the Code

Ensure your keys are stored far enough away from the car when parked to prevent "parasitic" drain.