There was a hardware issue, Toyota told their engineers one of the boards would have ECC RAM, but went cheap and used non-error-correcting RAM, but that wasn't the primary issue. After the court case ended, the code was subjected to static analysis by various researchers and a litany of problems were immediately found. Race conditions, uninitialized values, lack of fail-safe structure, spaghetti code, etc. I read a much better summary article awhile back that talked about automotive industry standards for embedded design and the working environment at Toyota (where developers had no static analysis tools, and didn't even have access to a bug tracker), but this article covers some of the points. The software was definitely at fault in many of the cases that killed 38 people:
That article makes a clearer picture of the issues you were hitting upon. Especially the later software audits. Perhaps you could add it to the Wikipedia page?
http://www.sddt.com/Commentary/article.cfm?SourceCode=201311...