Check Engine Light or MIL

Some lights are more important than others

Other lights warn of trouble: a condition you need to take care of. Some lights, like the oil pressure light require immediate attention. Others are less urgent: no need to immediately turn the motor off or get a tow truck or anything. The "Check Engine", or "Service Engine Soon", or "MIL" light is one of these "less urgent" warning lights. (MIL stands for "Malfunction Indicator Light") Here are some common MIL designs:

               

What turns the light on

The computer may go into a Limp Home Mode when this light is on.

Most of the earliest vehicles with computerized engine controls had an amber light which lit up with the words "CHECK ENGINE". This confused some customers, who thought it meant bad oil pressure, or high temperature, or something as serious. Some manufacturers changed the "wording" on the light to the less urgent sounding "SERVICE ENGINE SOON". Of course then people thought it meant to change their oil or something.

OBD II

Because of this, many parts stores will read out the OBD II trouble codes free of charge. It also means your local independent shop can "keep up" with code scanning equipment more easily.

As to the standardization of terms, everyone has agreed to call the light which indicates a computer malfunction a Malfunction Indicator Light, or a "MIL" .

As to the wording on your dashboard, there will no doubt be different wordings. Some cars I've seen have an amber picture of an engine that lights up.

What if you don't know what a light on the dash means?

INTERMITTANT MIL LIGHT

On some cars the MIL light will go out when the computer problem goes away, or soon after. On others you must use a scan tool to turn the light off. Some cars can set an evaporative emission control code if you leave the gas cap loose: some codes are more important than others. If a MIL light goes out, the code will still be stored in the computer as long as the battery in the car stays hooked up. On some of the newer cars the codes stay in memory even if you remove the car battery.