Audio Systems: rear camera, toyota 4runner, negative pulse

Question
2011 toyota 4runner  JVC/Densi satnav/4-disk stereo.  The unit has a large screen for the maps and displays back up camera in Reverse.  How easy would it be to wire a switch to turn on camera on demand,  to see the trailer I am towing for example.

also, do the units get firmware upgrades from sattelite downloads?  Once or twice a year I will turn on the car and it will say "system loading do not power off"  and after certain settings have been reset.  My station memories and destination file are still intact, so I don't think it is a memory power fault.

Sincerely,
Jeff
Green Bay WI

Answer
The camera its a negative pulse you need to find the wire that goes from the shifter to the radio and add a switch there that will send a negative signal to the radio, this way the camera will turn on, you have to diode isolate the wire , if not it will turn on the white reverse lights, the diode needs to be 1 amp

yes there are updates but they are more often i will say 6 times a year