The check engine light is a malfunction indicator light that a computerized engine-management system uses to let you know that something is wrong. The check engine light is a pictogram of an engine that illuminates either yellow or red. This indicator light works in two stages: steady when there is only a minor problem and flashing when there is a severe fault.
Below are some brief explanations of six of the most common check engine light causes.
- Loose gas cap: One of the most common (and easiest to fix!) causes of your check engine light turning on is a loose gas cap. The gas cap is important to your car’s fuel delivery system because it prevents the gas fumes from leaving the tank, and in doing so, it keeps the system under the correct pressure.
If you noticed that the check engine light turned on right after you filled up with gas, it’s entirely likely that you didn’t screw it on tightly enough, or you might have forgotten to replace it at all. Luckily, all you need to do to check is pull over, tighten the gas cap and see if that fixed the problem. If not, talk to your local auto repair shop. It may just be that the system needs a nudge to reset.
- Failed oxygen sensor: The car’s oxygen sensor regulates the mixture of air and fuel that enters the cylinder. The sensor sends data to the vehicle’s computer regarding the amount of unburnt oxygen in the exhaust system. The immediate effect of a failed oxygen sensor is the increase in the car’s fuel consumption and damage to the spark plugs and the catalytic converter.
- Failure of the catalytic converter: A catalytic converter turns the carbon monoxide produced during the combustion process into carbon dioxide. If the catalytic converter fails, it will set you back a few hundred dollars for a replacement. Regular maintenance should keep your catalytic converter in good working condition, sparing you the cost of replacing it.
- Spark plug and ignition coil problems: The ignition coil supplies the electricity that the spark plugs need to ignite the mixture of fuel and air. Newer cars have a single coil for each individual spark plug, which is different from the older models that have a single coil for all the spark plugs collectively.
If there is a malfunction in the ignition coil, the spark plugs will not be able to perform their task of igniting the gas-air mixture. Spark plugs can be worn out after a long period of use. In both cases – ignition coil malfunction and worn out spark plugs – the check engine light will turn on, and you need to find and correct the problem.
- Issues with the spark plug wires: The electricity generated by the ignition coil needs to be transferred to the spark plugs through the spark plug wires. You can tell when you have a problem with your spark plug wires when there is a significant drop in the engine’s performance, or the car has a rough idle. Replacing the spark plug wire will cost you approximately $50 per set.
- Bad mass airflow sensor: The mass airflow sensor watches the amount of air that enters the engine. Symptoms of failure in the mass airflow sensor include trouble starting, rough idle, and lower gas mileage. A bad mass airflow sensor will trigger the check engine light.
When you first notice that your check engine light is on, act quickly to diagnose the problem. Waiting could cause permanent damage to your car.