We have a 1992 Ford Taurus. The yellow “Check Engine” light on the dashboard panel has come on a few times lately, after we’ve been driving a while. Does this have a legitimate function, or did Ford put it in to ensure service calls from all Ford drivers?
You should be able to go to any large auto parts store and have them diagnose it for free. It means something’s wrong; it doesn’t mean you have to take it to Ford to have it fixed. It could be anything, though, from an oxygen sensor to a throttle body sensor to an exhaust leak.
It can mean that the computer caught a code, or a sensor tripped, or any number of things. Get the code read by a mechanic to see what the problem is.
One very basic thing to check when that light comes on is your gas cap. If it’s not secured properly, it will often trip the “Check Engine” light.
What Santo Rugger said. Find out what it’s responding to, then come back and ask us how to fix it. 
You can have them read the trouble code for free. Reading the trouble code and correctly diagnosing the problem are often not the same thing.
Not on a '92, that car has an OBD1 system and is not all that smart. Most, if not all “good” shops can read this. Time to bring it to a shop or a well trained independent mechanic.
Any where near Rochester NY.?
“Check engine” lights have been standard on all cars decades, not just Ford. They do have legitimate function, which is to make the driver aware that the onboard computer has recognized a problem in the systems that it monitors. Some such problems are serious or potentially serious, others are comparatively trivial. My suggestion is to have a competent shop evaluate it. There are parts store that will read the trouble code for free, and occasionally that’s beneficial, but reading the code is usually just the first step in identifying the actual problem. For example, if the code description is “low EGR flow,” they’ll suggest you replace the EGR valve, but that code is usually caused by clogged EGR passages in the engine or a leaking EGR hose. Generally, you get what you pay for.
Meh. The “Service Engine Soon” light has been on in my 97 Sable for 2 years now.
This is a 17 year old car with an old computer. My guess is, like some others have said, that even if an auto parts shop will diagnose the code, that will be pretty vague.
My suggestion (aside from the real one, take it to Ford), is to buy two bottles of Gumout (or a similar product), put them in your gas tank, and maybe whatever is getting stuck or tripping your computer will dissolve and burn away.
SFP
A better question is why can’t they just have a digital LED readout of the code on a car? It’s 2008 for crying out loud. My car has three on-board computers and the best they can do when there is a problem is turn a light on? Then I have to chug down to the autozone and beg the dullard behind the counter to check it out. I know the computer just reports a code, and doesn’t actually always state the problem, but it’s technically feasible to display the code, so why don’t they do it?
Good question, Fandango. And we HAVE used some additives in the gasoline, that we can buy at the 99c store… 
Some vehicles do, but you have to know the trick. Most Jeeps do. On my Wrangler, I turn the key on and off 3 times and it displays the codes on the odometer.
You can do what I did to my '95 Ranger: put a piece of black electrical tape over the “Check Engine” light.
(So far, so good. knocks on wood)
You won’t pass the emissions test in my state if your check engine light is on.
Until I noted the “WA” in your profile, I was going to ask where in NJ you lived.
VCNJ~
As was said below, I guess they don’t have mandatory regular inspections where you live. That would never pass smog check where I live.
Ed
California is that way, too. Biennial smog checks are required to register a vehicle, and the Check Engine Light being on is an automatic fail.
(Also a Fail is the CEL not coming on during the self-test on startup - so cutting a wire or removing the bulb won’t work, either.)
It is on constantly in my Mother’s Buick (and the previous one she had). It’s just that the gas cap isn’t on tight enough. But if it is tightened any more, she can’t get the cap off to fill the tank (she’s 85, and has some joint problems in her hand). So she just drives the car, and ignores this useless light.
I’ve been living in NJ too long when I start thinking, “What the heck is an 85-year old woman doing working at a gas station?”