good Techstream vendor?

Techstream, the software, is a Toyota product. Sort of by definition, the "good Techstream vendor" would be Toyota.

The software will work on a Windows laptop, and you need some J2534 dongle to plug into the laptop and connect to the car. There are a bunch of those, in a range of prices. The one Toyota themselves test Techstream with and will answer questions about is the DrewTech Mongoose (pro?), around $495 last I checked.

At the other end of the price spectrum, there was a company called XHorse that at one time made a more affordable J2534 dongle called the XHorse Mini VCI. You can't buy a real one any more (unless you find somebody who had an old one) because AFAIK it was wiped out clean by counterfeiting; there seem to be multiple makers of counterfeit "XHorse Mini VCI" and they all advertise as "XHorse Mini VCI" and show up as such when plugged in to your laptop, and they sell for incredibly cheap and some of them work and some of them don't, even from the same maker or seller.

There are also knockoffs of the Mongoose (called the Mangoose) selling around the same price as counterfeit Mini VCIs do. I don't know much about it.

There's an outfit called VxDiag selling their "VCX Nano" and I think it's around $80.

A US company in California develops the Tactrix Openport 2.0, which I've posted about before. You can still buy real ones of those, if you buy from Tactrix's web site; I think they are $169. Google will also find you counterfeit ones for way less. Please don't buy those; when we have a company that actually still does develop its product, we'd rather not wipe them out as happened with the Mini VCI.

If what you want to spend is Mini VCI money, please buy a Mini VCI, since the damage to its original maker has already been done.

My Tactrix dongle works very well with my Gen 3. I have seen some issues using it on a Gen 2 (for some functions on a Gen 2, I've actually seen a Mini VCI work better). I got the Tactrix after parting with my Gen 1, so I have never had a chance to test it with that.

 

I have a ScanGauge also. It's nice for driving around and watching a few extra gauges, but it's really impractical for working on the car. The only XGAUGE definitions for it are the ones that were painstakingly reverse-engineered by members of the community (chiefly Graham Davies and vincent1449p, you can read the history). Not all of them are completely verified. The Prius (especially Gen 1!) has multiple networks with ECUs on them that communicate using different protocols or bit rates, some of which the ScanGauge will never be able to connect with or even detect.

That's just on the data-reading side. On the side of the active tests and commands you can issue with Techstream to the car, last I knew, very little had been reverse-engineered for ScanGauge or for any other non-Techstream solution. (People who reverse-engineer protocols are usually a little bolder about experimenting with commands that read stuff, and not as bold about sending their car commands like "execute operation 17 with parameter 2F" just to find out what it does.) For a lot of service needs on the car, you'll either end up using Techstream, or taking the car to someone who uses Techstream.

If the Mongoose dongle is outside the price range you want, then there are considerably cheaper dongles available. The counterfeit Mini VCIs tend to be around $30 or less.

Strictly speaking, the dongle and the software are separate; the way to download the most up-to-date and official software is from Toyota, and activate it by subscribing to TIS ($65 winds it up for two days). On the other hand, some of the less-official dongle vendors may be throwing in software, which might not be the most current version (but a 2001 isn't the most current car, either), and might have some other differences from stock. One hears a lot about running those versions on an old beater laptop that is never used for anything important.