I'm not sure, but here is a guess, quoted from item 4 of the UR92 manual (since you have a UR90 already installed):
"If your layout has UR91s and or UR90s installed, re-set the LocoNet ID by
plugging in any DT402 throttle while holding down the EDIT Key. Release
the EDIT Key. Use the R throttle knob to set the LocoNet ID (00-07) you
want to use and press Enter to complete LocoNet ID set up. As simplex
and infrared throttles plug in to LocoNet, they will log on to the LocoNet
ID automatically and all three technologies will work together."
I'm guessing the 602 has an EDIT key.