Error 3 has to do with the Left Kernel Pop up character.
1) Check the alignment of the motor linkage with the sensor. The linkage may have moved and caused damage to the sensor. 2) If sensor checks out visually okay - Run an Input test to determine if sensor is reading correctly.
3) If sensor is faulty - Replace - If Sensor checks out okay - Skip to # 4.
4) Check electrical connectors to motor and ensure motor is receiving power. Run an AUTO TEST to determine to the motor is working correctly.
5) Check (or) replace the motor driver board.