Back in the mid-1980s, a few car makers experimented with talking cars. Your new Nissan 280Z could tell you things like, "lights are on" and "door is ajar." The voice was female, soothing and utterly annoying. Most drivers disabled the feature immediately. It's time to resurrect the talking car technology to do something useful, like replace the unnecessarily oblique "check engine" light that tells drivers absolutely nothing except that everything in front of the dash and behind the bumper could fail at any moment. There is specific information behind the drab and general message, and it doesn't take that much work to get at it.
Go to Autozone, or any chain auto parts store in your area. They have scanners and they're not afraid to use them. These stores love do-it-yourselfers, so they'll scan your code for free in the hopes that you'll attempt the repair yourself and buy your parts from them. Some locations hand over the scanner and let you do it yourself, while others will walk out to the parking lot and do it for you. They can also turn off the light while they've got the scanner connected, though it will come back on in a few miles if the underlying problem persists.
Go ahead and buy the dang scanner. The price of an On Board Diagnostic 2 (OBD2) scanner has come down dramatically since it became the standard in 1996. It will pay for itself over time.
Try low-tech methods if you really can't afford a scanner, and your car doesn't run well enough to get you to Autozone. There are bizarre combinations of steps for most vehicles that will tell you what the underlying error code is. OBD2 cars often display the codes on the odometer if you hold the trip and/or reset buttons and turn the key from "off" to "acc" or sometimes "acc" to "run" three times in succession.
Check with a mechanic or auto parts store over the phone to confirm the model-specific steps required to display the codes in your newer car.
Older cars (pre-1996 OBD1) will flash the check engine light and communicate the code to you as though they are sending smoke signals. Turn the key to "on," but don't start it. Wait three seconds, then stomp the accelerator all the way to the floor five times. Wait just a second, then depress the accelerator fully for 10 seconds. The "check engine" light will begin to flash, pause, then flash again. Write down the number of flashes, the do a search for your code online or call the auto parts store or mechanic to look it up for you.
