Yeah, that’s very understandable. But here’s the problem: If you do it yourself, then they’re going to deny future warranty claims if they can at all point to what you did as a potential cause of whatever’s wrong with it.
I agree with those who say you probably shouldn’t get a lawyer because it’ll be hard to recover enough to pay the lawyer, much less your damages. However, the blatant lying from your dealership would warrant a complaint to your state’s Attorney General. And many businesses are afraid of the AG, because the AG is a lawyer who’s free to sue any business he/she thinks deserves it and who doesn’t have to worry about collecting enough damages to make a profit.
If this dealership is feeding you BS like “it’s learning how to start,” then it’s guaranteed you are not the only customer they are screwing. The more customers who complain to the AG, the more likely the AG is to take action against them.
Finally, while I personally find social media to be the height of obnoxiousity, it can be a useful tool in cases like this. Start posting on the dealership’s Facebook, Twitter, Instagram, etc. Ask them why they’re refusing to service your truck under warranty. If that doesn’t bear fruit, go to Toyota’s social media pages and ask them why they’re letting the dealership get away with refusing to honor the warranty.