that is a very serious comm problem (Im sad for you, scary code)
reset it and see if it comes back other sysptoms, low battery
just finished jumper cable jump starts, or other odd battery issues???
short answer: take it to Toyota.
U1100 is seatbelt controller
Lost Communication with Clearance Sonar Module
i cant find much on U0100, are you very sure that is it?
DTC U0100 Lost Communication with Engine Control Module
1: check all fuses. using and ohm meter (restance low range) for 0 ohms.
2: check battery voltage running engine and not.
12.6v key off, 13.3 to 15v running, if not charge system failure.
3: pull battery minus lug for 1hr. and put back, keep in mind you can lose radio codes. or dead radio for lack of radio pw code.
4: re-seat all CAN buss modules in car, 1 by 1one battery minus pulled.
PCM, BCM , all off them. reseat means pull connector to it and put it back.
It might just be a random glitch, that all comms see, all the time on all networks. Unknown, glitch. (CRC failure)