Ford Repair: Sable emission controls, ethanol blend, autozone

Question
I have a 2002 Sable LS Premium Wagon that has been trouble free since I purchased it new in 1/03.  I have burned ethanol blend ever since I purchased it here in Nebraska cuz ethanol blend fuel has always been cheaper than plain regular gas.  That is until recently!  A couple of weeks ago I drove to MN, a distance of around 400 miles.  I used regular gas on that entire trip. On the return trip about 25 miles from home, the yellow engine light came on and has remained on ever since.  I took it to the Ford dealer a few days later for a 30,000 mile maintenance and for analysis.  Since they wanted $85 just to diagnose the problem and since the auto's manual suggested to give it some time to go off on its own, I deferred the diagnosis.  It is still on and the car seems to be running normally. Should I be concerned? (Most of my miles are "around town".)

Answer
The only way to know what caused the CEL to come on is to check the codes. If you have an Autozone parts store nearby they still check codes for free. I don't recommend you buy anything from them, tho. Otherwise you will have to pay a shop to get the codes. Once you have a code(s) let me know what it is and I can advise you further. Depending on the code you could drive to China and back and the light probably won't go out. There are only a few codes that can turn the light off, the most common being a loose gas cap code.

Autozone provides a service for free, but remember that they are in the business of selling parts, so they might suggest a part to fix the code. Having the code is only the start of diagnosis, it doesn't tell anyone which part to replace, regardless of what the parts store may tell you.

You should also keep in mind that your vehicle was not designed to run on ethanol, no matter the price.