I got my i980 for $120 on Amazon. There's an MBii model for $160 that has a few more capabilities like dealing with SBC. Read the reviews on Amazon, there's a ton of info to be had there. I think peachparts carries it too but you never know if it's actually in stock or until after you purchase lol.

Yes it can read and clear 722.6 transmission codes. From what I remember, it doesn't work with the w210 and the first gen SLK because those cars have a weird canbus architecture. Later cars were standardized. Everything else after that up to about 2012 is game. The MBii is good to about 2015 model year. There's a lot more info in the Amazon reviews. It def works with my w203. I bought the w203 stuck in limp home mode and the first thing I did was get the i980 to read and clear the transmission codes. It did that beautifully.

I think mbii also works with sprinters and smart cars, i980 doesnt.

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CENSORED due to not family friendly words