According to the "GM Service Manual" it says: "Connect a scan tool to the vehicle using the pass-thru This method requires connecting the scan tool to the vehicle, Then connecting the Techline Terminals RS-232 cable to the scan tool.. "
Tech II is connected to a computer using TIS2000 software, hence the needed dongle cable from the Tech II scanner to the computer running TIS2000 (connected in on a RS232 port).
This allows you to download the needed programming from GM directly for the RCDLR in the first place via/to the computer running TIS2000, then push it through the tech II to program the RCDLR through the OBD II port once the RCDLR is mounted in the car.
Note: some have had luck with a USB dongle, instead of RS232 Tech II dongle cable, but don't bank that you will have the same luck and best to have a computer that has a RS-232 port to run TIS2000 on.
Important: Prior to programming per the information below, the Radio and HVAC Fuses MUST be removed and the ignition must be in "Key On Engine Off Mode" The radio and HVAC fuses can be located in the BCM fuse block on the passengers floor electrical center. One of the fuses is labeled RDO/S'BAND/VICS and the other is labeled HVAC/PWR SND.
Program the RCDLR with revised software using TIS-2-WEB "Pass Through" method. When programming, it is required to select "Replace and Reprogram ECU".
Important: If the programming procedure does not finish successfully and the RCDLR appears to be in a "locked up" state do not turn off the ignition, follow the directions below...
The RCDLR can be reset by removing the RCDLR fuse (#11 in the UBEC) for at least 30 seconds or longer and then reinstalling it. Once this fuse is reinstalled in the UBEC, there will be a 2 minute window to restart the programming of the RCDLR through TIS2WEB. Failure to restart the programming of the RCDLR through TIS2WEB within 2 minutes may cause programming to fail and this procedure will need to be repeated. It is recommended that the Tech 2 remain connected to the vehicle and that the TIS2WEB application is open and ready to program the vehicle prior to reinstalling RCDLR fuse #11 into the UBEC.
This video will walk you through both stand alone, and pass through programming (go to 8:30 for pass through and note that the op is using a tis2web disc to access the needed programming, instead of pulling it down over the web).
And again, As for the latest RCDLR updates, tis2web is needed for that to pull the needed program; unless you can get your hands on a tis-2-web legacy disc current enough for your car and there are not any updates from that point forward from the disc.