VXDIAG VCX NANO Multiple GDS2 and TIS2WEB will work right out of the box without a GM subscription, since the GDS2 version you get with it, does not connect to GM, so the “VM” GDS2 program does not need a GM subscription to work.
So with it, it will give you the DTC codes to begin with, and you can go into the code directed modules to check them to see what the problem is, what needs to be replaced or corrected.
So once you have GDS2 running and the Gm nano connected to the car and PC, step one is to go into to vehicle diagnostic, and use read vehicle wide DCT and id information. This will list the Dtc to start with.
Now back out of that menu, and go into module diagnostic, and depending which module the DTC code pointed you at, go in that module to read it’s data/trouble shoot the problems.
Again so long as you don’t need a brand new module that will need to be initially firmware vin flashed to lock it to the car, or need to get into a security menu to say learn a fob into the car (both part of the SPS program, not the GDS2 program), you don’t need a subscription to GM.
If you do need to use the SPS program for the above, then you can get at least a three day subscription to GM, and it will load the needed subscription locked programs to your computer as you use them (your VM GDS2 program will be locked away in it own little folder safe, independent of the programs that the subscription programs that will be downloaded to your machine, and will only work while you have an active subscription to GM).
Really, check around in your area to see Who has a Clone MDI with Vm GDS2 to give you a hand. This will not only give you chance to see how the device and GDS2 is used, but will make short work of figuring out the problem of the car. Trust me, once you see the what GDS2 can do with the car, you will want it for yourself as well.
On the C6’s, by going through just the voltages of each module, I can tell where there is a electrical problem, before the problem causes a lose of communication down the line instead.
Hence if the ECM has a voltage of 14.3 with the reast of the modules , yet the RCDLR has a voltage of say 13.4V, know that there is either a bad connection to the module, ground point problem, or that the board has a cold solder joint that needs to be re-soldered; before it starts to cause DTC problems isntead.
On the F55 module, again a snap to catch problems before they happen to start throwing DTC codes, since I can check ever sensor for it’s voltage too. Hence say three of the level sensor are reading 2.1 volt, but one is reading 1.2 volts, you know it has a problem that needs to be resolved before it causes DTC codes next.