Here is some information to solve the issue.
E3 error code indicates a indoor fan speed malfunctioning which can be affiliated to a bad indoor circuit board or a bad indoor fan motor.
In this case, you can first make sure that the indoor or the outdoor fan are not blocked and can spin freely. Second step would be to test the circuit board and third is the fan motor.
To test your indoor and outdoor circuit board,
you will simply have to verify the voltage frequency using a digital multi-meter. You will have to set your device on DC (direct current) and verify the voltage between terminals L2-S or for some models it would be between 2 and 3 on the outdoor terminal block. The result should be fluctuating between -50 and +50 VDC alternatively. If the the voltage fluctuates with only positive or only negative numbers, this indicates that the outdoor mother board will have to be replaced. If the result remains constant and there is no fluctuation at all, the indoor board will have to be replaced.
To test the indoor fan motor,
Release the UVW connector. Mesure the resistance of the U-V, U-W, V-W. If the resistance is not equal to each other than there is an issue with the fan motor and it will need to be replaced. Otherwise go to step 2.
Power on and when the unit is in standby measure the voltage of pin4-5 in the feedback signal connector. If the value is not 5V Change the PCB (Motherboard). Otherwise go to step 3
Rotate the fan by hand, measure the voltage of pin 1-5, pin 2-5 and pin 3-5 in the feedback signal connector. If any voltage is not positive fluctuation, the fan more will need to be replaced.