"This makes the manual very confusing..."
Same thing I said when they first started putting the different sonar type units together like this.

Not sure why the 455kHz 2D sonar would not be working. If it were software related, all DI model unit owners would be posting about this. Hard to believe though that toofuss has two units or transducers with the same problem though.

History lesson of the day: Humminbird first used the 455kHz frequency as a conventional 2D sonar beam way back in 1988 in the TCR 101, TCR ID-1 and TCR Color 1 units then later in the Platinum 120. These had the option of the (standard) 16 degree beam or the wider 40 degree beam.