The argument for DRM in the car MIGHT fly in cars that are leased (which in my lay-person's brain sounds somewhat similar to a license for using software), but there can be absolutely no reason for preventing me from accessing information on something that I own outright.
Its not like I bought a license to drive the car (that was provided freely (sans a few yearly fees) by the government of my state), I own the metal. What possible argument can there be for preventing me from reading the information in my car's engine?
"If you can, help others. If you can't, at least don't hurt others." -- the Dalai Lama