My recent experience with my Golf prompted this question ...
My VW is a Motronic and has a MAF sensor. I've been chasing a recurring problem where it runs fine with no codes and then suddenly refuses to run at any slower than about 2500 RPM. It was throwing IAC out of range and Lambda out of range before I replaced the O2 sensor. Then all seemed to be well - I test drove with no codes. Turns out the MAF was going bad, but the computer trusts the MAF more than it trusts the IAC or Lambda, so it points to those first. On Sunday the MAF shorted and the engine hardly ran, so I limp home and park in the garage ... it's stumbling at idle, and I unplug the MAF, and suddenly I have a smooth idle and the engine revs from idle perfectly. The CEL is on, but the engine runs fine.
So this made me wonder, with the GM computer, how much can go wrong and it will still run? I know it has a limp-home mode, but what parts failures are guaranteed fatal and what failures can be limped on with?