As of firmware version 3.11, the Aries drive will indicate an E54 (encoder loss) during autocommutaion with a pattern of 5 green and 1 yellow flashes of the left LED. The right LED will be red.
Here is part of the release notes:
Drive will now fault with E54 (Encoder Loss) during auto-commutation if no encoder is detected (signified by both encoder phases being close to 0 volts). This Fault (E54) is signified by a new sequence of 5 green flashes and 1 yellow of the upper LEDs. An encoder loss fault will also occur if no encoder movement is detected during the final auto-commutation move.
The drive will now flash the lower LEDs green and red at approximately 2Hz during autocommutation.