You’re driving down the road and out of nowhere your check engine light suddenly comes on. Can you keep driving, or do you need to pull over right away? Because check engine lights can mean several different things, it’s always best to stop the car as soon as you can safely do so to make sure nothing dangerous is going on. The check engine light can mean something as simple as a loose gas cap or something more serious like a failing catalytic converter. Here are some of the most common reasons why the check engine light may come on.

1. Loose or Broken Gas Cap

When your check engine light comes on, the first thing you should do is check your gas cap since this is the easiest problem to fix. When your gas cap is not properly secured, it sends an error message to the vehicle’s computer to let it know that the pressure in the gas tank is off. Check your gas cap to see if it is loose, cracked, or chipped, as this could be the reason for your check engine light. If it’s loose or just not on the right way, re-secure it and then restart your vehicle to see if the light has turned off.

2. Damaged Spark Plug or Ignition Coil

The spark plugs in your vehicle ignite the fuel and air mixture in the cylinders to start the engine. The ignition coils generate the electricity that the spark plugs use to do their job. Your vehicle may have one or several ignition coils depending on how old it is—classic cars have only a single coil, while modern vehicles often have a separate coil for each cylinder. A damaged or malfunctioning spark plug or ignition coil will affect your vehicle’s ability to turn on and run properly, and it will cause the check engine light to come on. Luckily, spark plugs and ignition coils are fairly easy and cheap to replace.

It’s important to note, however, that spark plug and ignition coil issues can only cause the check engine light to come on in gasoline-burning vehicles, as diesel engines don’t have spark plugs or ignition coils.

3. Faulty Spark Plug Wires

Faulty wires in the engine, especially those connecting the ignition coils to the spark plugs, can cause the check engine light turn on. When these wires don’t properly transfer electricity where it needs to go, the fuel and air mixture in the cylinders can’t ignite, and the engine can’t run. If your vehicle has faulty spark plug wires, you may feel a rough idle, notice poor engine performance, and experience lower gas mileage. An auto mechanic can easily replace faulty spark plug wires, and it should be a relatively inexpensive repair.

4. Failing Oxygen Sensor

The oxygen sensor in your vehicle measures the amount of unburned oxygen in its exhaust system. This data is sent to the vehicle’s computer and is used to regulate the mixture of air and fuel that goes into the cylinders. When the oxygen sensor fails, it may trigger your check engine light to let you know something is wrong. Your engine will still run even when this sensor fails, but it will burn through fuel more quickly than usual. If left alone for a while, a bad oxygen sensor can cause other components, such as spark plugs and the catalytic converter, to become damaged as well. A vehicle with a bad oxygen sensor will also likely fail an emissions test. A mechanic will be able to tell you if the oxygen sensor is the reason your check engine light is on and will be able to fix it before it causes further damage or makes you fail an inspection.

5. Mass Air Flow Sensor Issues

Your check engine light may turn on if the mass air flow sensor fails. This sensor is part of the engine-management system and monitors and regulates the amount of air entering the engine. Without a functioning mass air flow sensor, your vehicle will not be able to adjust to changes in altitude and will experience trouble starting, a rough idle, and possibly a sudden change in the throttle pedal position. Mass air flow sensor issues can also cause stalling and noticeably lower gas milage. If you keep driving with a broken mass air flow sensor, you will likely cause other engine parts to break as well.

6. Failing Catalytic Converter

The catalytic converter is part of the exhaust system and turns carbon monoxide into carbon dioxide. Its failure can usually be prevented with regular vehicle maintenance. If the catalytic converter does fail, it’s typically because other issues and maintenance tasks have been ignored. Another issue will usually trigger the check engine light before it causes the catalytic converter to fail, so be sure to get problems fixed before they can damage this component, especially because catalytic converters can be quite expensive to replace.

7. Vacuum Leak

The check engine light can come on if your vehicle has an issue with its vacuum system. This system performs a variety of functions, such as helping boost brakes and lowering harmful emissions. In addition to the check engine light, other symptoms of a vacuum leak include your vehicle’s idle surging and settling at an abnormally high rpm. Vacuum leaks usually occur when hoses dry out and crack as they get older, especially when after having been exposed to extremely high or low temperatures. Loose connections and cracked fittings can also cause vacuum leaks. New vacuum lines are usually inexpensive, but a lot of labor may be required to find the source of the leak.

8. Aftermarket Alarm Issues

If an aftermarket alarm is installed incorrectly, it can mean disaster for your vehicle. The alarm may drain the battery, prevent the vehicle from starting, or trigger the check engine light. If in addition to the check engine light you’ve also experienced issues with your alarm being too sensitive or going off randomly, then the problem is likely that it was not properly installed. You will need to have an experienced mechanic fix, reinstall, or replace the alarm. To avoid this headache, it’s always best to have the alarm installed properly by a professional the first time, even if that means paying a little more upfront. In the long run, this will save you time, money, and the stress of a malfunctioning alarm wreaking havoc on your vehicle.

9. Clogged Exhaust Gas Recirculation Valve

The exhaust gas recirculation system redirects hot gases back to the combustion chambers to help warm up the fuel to make it easier to burn, which helps the engine run more efficiently. This system also reduces the amount of nitrogen oxide released by the engine, lowering emissions. The exhaust gas recirculation valve can become clogged or fail, which means it will not work properly and may cause the check engine light to come on. If the valve is only clogged, it’s simple to remove, clean, and reinstall it. Otherwise, a new valve can be a little costly to replace.

10. Bad Battery

Everything in your vehicle is affected by the battery. It’s needed for everything from starting the engine to powering the lights to running the radio. Car batteries do not usually require maintenance, but a bad battery may die quickly and need to be recharged or replaced. A dying battery will trigger your check engine light or a battery charge warning light. Charging or changing a battery is an easy task to do on your own, but you may want to have a mechanic help you so they can check the connections for additional issues.  

Get Your Vehicle Checked by An Experienced Knoxville Mechanic

If your check engine light comes on, don’t ignore it! This warning light will usually first turn on when the vehicle’s computer notices a small issue in the engine, so you should get the issue fixed before it becomes a much more serious and potentially dangerous problem. Auto and diesel mechanics have diagnostics equipment that they can use to determine the exact reason for your check engine light. An experienced mechanic will then be able to repair or replace the necessary components to solve the issue. Certified Diesel Solutions is a Knoxville mechanic company that can help you figure out the underlying cause of your check engine light coming on and any other issues you may be having with your vehicle. We want to help you solve the problem as quickly and painlessly as possible to get you back on the road in a vehicle that can safely get you where you need to go. We have all the latest tools and diagnostics equipment as well as expert ASE-certified auto mechanics and diesel mechanics who have the knowledge and experience necessary to provide the best solution to your problem. Reach out to us today to schedule vehicle repair or maintenance with the best mechanics in Knoxville, TN. Give us a call at 865-964-6598 or fill out our online form.