I have no first hand experience but I was just looking into one and Innova appears to have a wide product offering with high average reviews on Amazon. http://www.innova.com/
I was just looking at one of these at my local auto parts store. They had Bosch units which are also the ones who make the Tech 2 used at GM dealers I'm told. It was well made, but was some $40 cheaper on line.
The latest Matco flier has one I'm thinking of getting, for $299. It looks like it provides a lot of info for the money and a lot better than any of the other "generic" ones I've seen, plus does ABS and SRS codes too. Flier says "for a limited time" only, not sure what that means. Might buy one this week when he comes.
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Erik
69 Camaro
Several other things with wheels and engines
I've never used one these before and assume that you have to input what vehicle your troubleshooting. How do these things work in an old car with new technology because obviously a 68 Camaro with an LS isn't gonna be an option to choose from?
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Chris
1968 Camaro: DSE tubs and sub frame connectors, Chassisworks G-Link rear suspension, Speedtech upper and lower control arms, Chicane front coilover conversion with QA1's, Baer brakes, 18" Forgeline SO3's, Vintage Air, 6.0L LS 417 rwhp, 4L65E, Moser 12 Bolt w/3.73's.... http://www.cardomain.com/ride/2391864
I've used several. Some auto detect and done you input the info yourself. For my car, I choose the vehicle the ECM is from and it works fine. One of the nicest I used was the Snap On Solus, but it's very expensive.