I guess Snap On wanted to make it so you only pay for what you are using, remember this $hit was expensive when in production. So now you need to find these cartridges that work for your car, wait, you are not done yet, you need these special keys that go with each cartridge. You only need a primary to access the computer, the troubleshooter tries to help you figure things out, I have not tried it as yet. Their are also 2 types of cartridges the primary and the troubleshooter (I guess that's what you call it). Later vehicles with OBDII functionality can used a generic cartridge but sometimes it's less detailed then the specific make/model/years type of cartridges. For example you need the Import Asian Cartridge to be able to look at the computer on Asian cars. These units require cartridges and keys to enable specific scanner functionality. So the good is their are plenty of these units floating around.
You just need to make your cable for a few bucks (at some point I'll show how to make one, it's pretty easy). You can find the Snap On printers on Ebay now and again, but if you look for the Seiko models (414 and 411 I recall) you can find them for under $50 bucks. It does feature a rechargable battery instead of the always dead 9v that the MT2500 has. They made a similar unit to the MT2500, the MTG2500 which has a larger color display, shows some graphics, but essentially the same unit. Snap On also came out with a bunch of better (and much more expensive) diagnostic tools so these were hitting the auctions like crazy. They were getting old and outdated and most of the new cars were getting too advanced to use them. At some point I saw them on Ebay for cheap compared to what they cost new.
Years ago I had a mechanic do some work on a car and he pulled out this RED BRICK looking thing from Snap On, very nifty looking and l though that's a cool tool, does all kinds of crap beyond the regular code reader/scanner. Their are lots of cool options out now since I picked up the INNOVA 3120, it does have OBD1 and OBD2 or is that OBDI and OBDII? Never the less lots of new technology is out and some can use Bluetooth with your iPhone/Andriod and cost only a few buck with a low cost app (I have not yet tried them) all the way to the other end of the spectrum, the professional tools that might be made by Snap On, OTC, and other automotive manufacturers. It does the job resetting Check Engine lights and finding out what 's up with the car when the light does go on. I have an INNOVA 3120 Diagnostic Scan Tool that I use now and again. Snap On MT2500 Diagnostic Scanner Rebuild