so google adsense will pick the ads for you
This is correct. Adsense picks the ads, you don't. Depending on who visits your site, how they found it, what they like, what your site talks about, who pays the most, etc...
Bottom line, if your site is dedicated to cars and all the people who visit it are car fanatics, it is possible that adsense will show lots of ads for cars, car insurance, etc... but you can't really predict it, let alone choose. Their algorithms decide for you.
If you want to show a specific ad, this is typically done through affiliate marketing (CJ and the like, as you mentioned, but I don't think Toyota/Honda go through mainstream affiliate sites), which is not what adsense is about. Or a direct contract with the company that owns the product, but for that your site would need to have significant visibility already in its niche, IMO.