When my CAS failed a couple years ago I initially thought it was the ECU that had failed. They can present some similar symptoms, such as relays firing under the dash, erratic tach readings. There will be no spark, it would crank and not fire.
Mine failed pretty quickly, though - It died in traffic. I was able to start it again, but it only ran for a few seconds before dying again. I was able to repeat this a couple times, where it would fire and die, but I ended up having to roll it back down the hill I was on into a parking lot.
Try a spare CAS if you've got one available. If you've washed your engine bay lately it could have gotten wet on you.
