What Should I Do When The

"Check Engine" Light Comes On?

By Daryl Harwick

Daryl’s Automotive

 

What does the light mean?

First of all the Malfuction Indicator Lamp (MIL) may also be known as the Check Engine, Service Engine Soon or Check Power Train light.  Or it may be nothing more than a picture of an engine on your dashboard which is an International Check Engine Symbol, perhaps with the word Check.  

 

Anyway, let’s just use the term Check Engine (or CE) to keep things simple.

 

The CE light informs you when there is a problem somewhere in your car’s Electronic Engine Control System. The CE light is not only for the vehicle’s emission system as some techs would have you believe. This system basically includes all sensors, solenoids, valves, actuators etc. that your vehicle needs to operate correctly.

 

The Electronic Engine Control System is huge, and can include both engine and transmission concerns. The CE light is part of your car 's so-called onboard diagnostics (OBD) system. Since the 1980s, computers increasingly have controlled and monitored vehicle performance, regulating such variables as engine speed (RPM), fuel mixture, and ignition timing. In most cars, the computer also tells the automatic transmission when to shift.

 

When the computer finds a problem in the electronic-control system that it can 't correct, it turns on your CE light.   In addition to turning on the light, the computer stores a "trouble code" in its memory that identifies the source of the problem, such as a malfunctioning sensor or a misfiring engine. Call it the most misunderstood indicator on your dashboard, the CE light can mean many different things, from a loose gas cap to a seriously misfiring engine.

 

My check engine light is on, now what do I do?

While it doesn 't mean you have to pull the car over to the side of the road and call a tow truck, the CE light should not be ignored.   You should get the car checked out as soon as possible.   Ignore the warning and you could end up damaging expensive components.  The CE light can also be a sign that your car is getting poor fuel economy and emitting higher levels of pollutants.

 

The CE light does not mean you have to go the dealership.  Most independent repair shops can give you an idea of where the problem may be.

 

Some auto parts stores will even do what we call a quickie diagnostic test.   Then they will be happy to sell you the parts they think are related to your trouble code.  Be careful with that, because we have seen people spend hundreds of dollars who got nowhere just because their code was misinterpreted.  A true computer system diagnostic test is what you need.

 

Here is what to do as soon as it is safe to do it:

• Look for a serious problem that requires immediate attention. Check your dashboard gauges and lights for indications of low oil pressure or overheating. These conditions mean you should pull over and shut off the engine as soon as you can find a safe place to do that.

•Assuming it is not one of those very serious and immediate conditions, try tightening your gas cap. This often solves the problem. Keep in mind, however, that it may take several trips before the light resets. Some vehicles have a separate indicator that warns of a loose gas cap before the condition sets off the CE light.

•Reduce speed and load. If the CE light is blinking or you notice any serious performance problems, such as a loss of power, reduce your speed and try to reduce the load on the engine. For example, it would be a good idea to stop towing a trailer. Have your car checked as soon as possible to prevent expensive damage.

• Don't go for a state emissions test in a late-model car with a CE light on.   In the Baton Rouge area, it is an automatic failure, even if the problem is nothing more than a loose gas cap.   And don't bother trying to fool the inspection station by disconnecting the battery or using any other method to erase the trouble code to turn off the "check engine" light. Your vehicle ' s computer will let the inspection station know that its codes have been erased, and you will just have to go back again.
• If the CE light illuminates, it will either blink or remain constant, depending on the problem. Either way, you should have the vehicle checked by a mechanic but a blinking light indicates a problem that needs immediate attention.
• In late-model cars, a blinking light usually indicates an engine misfire so severe that unburned fuel is being dumped into the exhaust system, where it can quickly damage the catalytic converter.   This requires an expensive repair.

 

In general, if the light is steady, the problem is not an emergency, but you should schedule an appointment as soon as possible. Today 's automotive computers

often try to compensate when there 's a problem; so you may not notice deterioration in performance, even though your fuel mileage is suffering and your vehicle is emitting unacceptable levels of hydrocarbons and other pollutants.

 

For more answers to automotive questions call 769-2832 or shoot an email to  daryl@darylsautomotive.com .