Re: I hope it is heat tolerant
See the comment from Cuddles.
Higher temperatures do require things like thicker oxide and a process that doesn't create small bottlenecks in tracks which cause IR heating and atom migration. But modern semiconductors start off a lot more consistent than they did back in the day when I was working with JAN stuff. As I recall there was a scandal when it turned out Nat Semi had been sticking commercial ICs in mil packages and selling them to Uncle Sam, and not only was nobody the wiser till it was noticed that the paperwork had been fiddled, but that year they won a quality and reliability award from the government.
ECUs do have CPUs, 32 bit and a few tens of MHz, but they aren't usually liquid cooled. There are all kinds of mitigation I can think of, from putting them in the inlet air path in Diesels (which draw in a lot of air), to the liquid cooling used in the Prius.
One thing I do know is that electronics are far more rugged than the current wetware used to steer cars, which starts to malfunction outside the very limited ambient of 0-30C and is very prone to EDI - emotion and drug interference.