GM Tech2 is a diagnostic tool for the most part. It can be used to program out/in certain RPO’s in the BCM and can be used to bleed the ABS brake system without introducing air into the system. The extent to which it can be used to tune a Chevrolet C5 is that if you have a PCM Image that will work for your car you can save the current PCM Image and flash the new one you have onto the PCM. It cannot go in and individually change the tuning tables in the PCM as can say either EFI Live or HP Tuners tuning tools. But then those tools cannot touch the BCM either.
If you do or plan to do a lot of diagnostic work on your car it can be a worthwhile tool. Most of the diagnostic charts in the factory service manual assume the availability of a Tech 2. But you have to learn to use the tool like any other computerized diagnostic tool. It has layers and layers of menus to wade through. But in certain diagnostic situations it can be an invaluable tool because it allows you to turn on and off hundreds of computerized settings to aid in the diagnosis process.
GM intentionally dumbed down the capabilities of the Tech 2 to change things to avoid law suits due to an errant technician that changed engine or emissions settings that could result in engine damage or emissions violations.
GM Tech2, the bi-directional scan tool can access all the 10 computers in the C5 corvette. That means it can scan for DTC codes, allow the adding or removing of most accessory codes like turning off the mag ride shocks to install regular schocks, fixing window regulator problems, etc. For Bi-directional it can active the ABS system to flush the brake fluid, reset the Long Term Fuel Trims, eliminate the 1-4 shift on manual trans, etc. It cannot make changes (like a tune tool) to the transmission or engine management system. For the avid DIY’er it is a great tool.
In the C5, the “computers” (technically they are modules) and they communicate over the OBDII compatible DLC data bus to each other. The range from you radio to your ride control, to your HVAC system. Even the Bose head unit talks to the PCM and BCM through this bus, but the CD changer talks over a “private” data bus to the head unit.
The Sensor Modules that can be pulled up from the DIC are:
PCM, BCM, TCS, RTD, IPC, HVAC, LDCM, RDCM, SCM, RFA, and SDM.
Only those C5’s with RPO F45 or F55 will have RTD.
Reference: Here is a very useful Tech II Scanner pathing document that you can use to figure out how to get to the end result that you need to test.