Hey guys, just registered here because this thread had some decent and up-to-date information and figured I would share my recent experience with all of this...
I have been around tuning since the mid-90s, primarily SBC Gen-II LT1/LT4 stuff. Did my fair share of tuning LSx systems, enough to own a HPTuners with unlimited LSx credits along with OSes and enhancements. I have also tuned DFI, FASST, Motec, Haltec and everything else out there just about, including custom systems for auto-tuning...
We own a 2014 Cadillac CTS and a 2015 Cadillac ATS and I have HPTuners for both. I also know that tuning for these modern Gen5 engines is FAR from the old-school stuff, so much so we even bought Elite tunes for both Cadillacs from Trifecta Performance.
Well, the ATS is getting a "ground up" complete rebuild with new everything, including forged engine, transmission, transfer case, rear diff, front diff, axles, suspension, etc, etc. Because of this I needed a package that can reprogram the Transmission Control Module as well as the Transfer Case Control Module for the new parts.
Basically, I needed a solution to do not only SPS2 programming, but also be able to do configurations via GDS2.
There is no way I could spend $1100-1800 on a MDI2 setup or any of the other "authorized" setups and settled on a second-hand Mongoose-Plus GM3 cable. Needless to say it is HARD to find one of these used, but I got lucky. Then it seemed like it wouldn't get here, so I started looking into other options and I REFUSED to waste my time on the MDI2 clones or even the VCX Nano BS that is out there...
But I did come across a setup called OBDx Pro GT. It is billed as a J2534 compatible setup that supports the GM-specific protocols to use SPS2 and GDS2. Considering it was about 1/4 the price of a Mongoose-Plus GM3 I ordered it up. Took forever for them to ship, but finally got a tracking number.
Wouldn't you know it the Mongoose-Plus GM3 comes in the next day after I finally get tracking info for the OBDx Pro GT. I installed it, downloaded Techline Connect, spent over an hour allowing the installation to "settle in" and update itself properly. It is just amazing that something so convoluted and complicated can even operate properly, but after 5 different start attempts, updates, configurations and everything else it finally allowed me to launch it from the web portal and came up and allowed me to talk to the vehicle.
I must say the Mongoose-Plus GM3 just flat out "works". I would expect it to be damn near identical to the MDI2 in that it is quick, responsive and everything works as expected. Using SPS2 or GDS2 everything just does what it is supposed to. The only issue I ran into was trying to use SPS2 to deal with the Transfer Case Control Module for reprogramming, but it would seem that GM has issues with SPS2 being able to talk to that module on MANY vehicles under SPS2, so I am not alone. GDS2 had no issues talking to it and configuring it for the different clutch electrical characteristics, which is all I really need, so I am all good for what I need the setup for.
A few days later I got in the OBDx Pro GT and decided to try it out as well. Installed all the software, configured it, and low-and-behold it works just fine in SPS2 and GDS2 as well. Not as quick and snappy as the Mongoose-Plus GM3, but per the OBDx people it is probably because the SPS2 and GDS2 software trying using OBD2 protocols that thier device doesn't support so it needs to "time out" and then move on to the protocols that are supported. Makes sense and I did not notice any lack of functionality outside of communications taking "just a little longer" than with the Mongoose.
Hopefully this information helps out others, since I knew the Mongoose-Plus GM3 was "approved" by GM for use with their software, but it is good to know that a much cheaper solution in the OBDx Pro GT ends up working just as well.
I just did not want to be at the mercy of the VxConfig manager BS "allowing" the VCX Nano to be used whenever it felt like. I like owning my hardware and knowing it will work whenever I want it to without "trusting" a company that has been quite deceptive in how thier product works and why you need to "license" it every 60 days or so... No thanks.
I will add that I am seriously impressed with how many operations are supported under GDS2 for maintaining and diagnosing modern vehicle systems. I can't see owning most any of the more complicated modern vehicles without this level of ability.