Car or truck Check Engine light, MIL light, Service Engine Soon light, Auto Advice

Some lights are more important than others

Cars and trucks come with warning and indicator lights on the dashboard. Some indicate normal operation, like the green arrows that blink when your turn signals are on, or the high beam indicator to let you know your headlights are on high beam.

Other lights warn of an abnormal condition that 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

When the computer senses a problem from one of it's sensors it illuminates a light to warn the driver there is a problem.

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

Recent Federal regulations have required manufacturers to have certain things in common with their computer controlled vehicles. These agreed-upon standards include universal data interfaces, trouble codes, and component terminology. These standards are called OBD I and OBD II. (OBD="On Board Data") OBD I was only used for a few years; most cars on the road have 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?

If you're not sure what a light means, you can use this rule of thumb: A red light is urgent, like the low oil pressure light . An amber light is less urgent. So if you have a "MIL" light on in your car, and it still seems to run fairly well, no need to stop immediately or call a tow truck. Just find out what trouble code has been set as soon as possible and correct the problem.

INTERMITTANT MIL LIGHT

On some cars the MIL light will go out when the computer problem goes away. 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.

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Thank you for visiting the ECONOMECHANIX WEB SITE. Please feel free to comment. We also serve the surrounding communities of Alachua, High Springs, Hawthorne, and Newberry! Gainesville has been my home since 1974, and I've loved Gvl and the Gators since I came here in the fall of 1974 to attend the University of Florida. I loved it so much I stayed and opened my car repair business. Originally it was out of the back of a 1963 Chevrolet wagon, but in 1977 a fellow mechanic and I opened an auto repair shop with actual walls, etc. I stayed in the same location for 26 years, and recently moved my operation to property I bought 15 miles east of Gainesville. I am doing most all the repairs myself now, having reduced my overhead from $1500 per month to practically nothing. I do work by appointment only. I mostly work only on my established customers cars, but I will occasionally take on new clients. E-mail me and I will either make arrangements to look at your car, or I will recommend you to someone who will.

George G. Scott, Jr.

"Check Engine" "Service Engine Soon" or "MIL" Light: What this light means and what you should do if it comes on

Some lights are more important than others

What turns the light on

OBD II

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

INTERMITTANT MIL LIGHT

"Check Engine" "Service Engine Soon" or "MIL" Light:
What this light means and what you should do if it comes on