Struggling with a rear view canera

Assuming the camera is electrically compatible with the radio, you may have to remove the terminals (with the wires still attached) from the 16-position connector supplied with the camera and install them in the existing 24-position connector, G83 (Navigation Receiver Assembly) or G89 (Radio and Display Receiver Assembly):

G83-11 or G89-11 (CA+)
G83-12 or G89-12 (V+)
G83-23 or G89-23 (CGND)
G83-24 or G89-24 (V-)​

Toyota’s Wire Harness Repair Manual (PDF, circa 2007) has the basic procedures for handling connectors, and the details specific to your car are in the Electrical Wiring Diagram, available by subscription to techinfo.toyota.com.

Your local public library sponsors free access for its patrons to the ChiltonLibrary service, which doesn’t have the Electrical Wiring Diagram, but it does have the Terminals of ECU and DTC C1622 sections from the Repair Manual, which might give you enough information, if you already know what each wire in the 16-position connector does.