Check Engine Light Came On, What's The Possible Cause?

When your check engine light suddenly makes a permanent appearance on your dashboard, make sure to check the following five areas of the car before you fork over the cash for a mechanical check up:

Reason #1: Faulty Spark Plugs

Spark plugs serve the purpose of transferring heat from the combustion chamber and igniting the fuel/air mixture into the engine. They are some of the easiest components to replace when faulty, but they're also prone to burn out.

If your spark plug cables and wires are even slightly worn out, or the spark plugs themselves are getting a little old, they will misfire and cause the Check Engine light to turn on. Take a close look at the spark plugs for any signs of damage, and replace them yourself to see if they are the reason behind the Check Engine light's appearance.

Reason #2: The Gas Cap is Loose

Many vehicles have sensors around the gas tank that go off when there is too much or too little pressure in the tank. If you haven't tightened the gas cap properly after fueling up, there can be too little pressure inside which sets off the sensor. Turn off the car, tighten the gas cap, wait a few seconds and start the car again; there's a good chance the Check Engine light will disappear promptly.

Reason #3: The Fuel Injector is Clogged

The fuel injectors can become clogged with dirt and oil, which means the gas isn't getting to the combustion chambers properly. The fuel injectors must be clean or they won't be able to spray the gas into the engine. If this is the case, you'll notice that it takes longer for the car to increase speed when you push down on the accelerator.

Having your fuel system flushed regularly is the best way to prevent this from happening; if it's been too long since you've had the fuel injection system cleaned, now would be a good time to get it taken care of - and it may just turn off your Check Engine light.

Reason #4: The O2 Sensor is Faulty

The oxygen sensor is responsible for measuring the amount of oxygen in the exhaust; it will send out a signal to your engine's computer to either add or reduce the amount of fuel being delivered to the combustion engine when you push down on the accelerator. If it's faulty, you will probably be getting really bad gas mileage, or you'll notice it's hard for the car to pick up speed. A faulty sensor will also make the Check Engine light turn on.

Reason #5: The Exhaust Gas Recirculation Valve is Dirty

The exhaust gas recirculation valve (EGR) is designed to reduce exhaust emissions by recirculating exhaust gases into the engine's intake stream. This process reduces nitrous oxide formation because the gas displaces some of the intake charge and cools down the combustion system. If this valve gets clogged with oil or dirt, or it starts to deteriorate, you might notice a strong smell of gas every time your start the car; this will also set off the Check Engine light.

If none of these causes are the culprit, you will need to pay a mechanic to run a computer check on the codes which will determine the root of the problem. These mechanical checks can cost between $60 to $200 depending on the make and model of your car, and the mechanic you go to.