Check engine came on 2 days ago, checked all fluids, OK. Running smooth, BUT...

Thanks for your speedy reply ! The strange thing is, and I am by no means discounting your "drive train" observation as that is THE #1 indicator, BUT, and bear with me, please... even AUDI-philes will tell you that the in-board computer might be slightly "over-tasked", as even a loose gas cap will set off the Check Engine (for good reason!). The strange thing is, that at the same time that this started, I lost the side and rear lights , as described, but ALSO, the audible signal that one has left the lights ON, when I turn off the engine and pull the key?? Being the weekend AND a holiday tomorrow to boot, the timing really sucks! BUT, hopefully, knowing that all fluids are good, battery is fine and charging, no over-heating, it might (PLEASE !!!) just be a computer glitch. Off to Church! Thanks!!