What Does Your Check Engine Light Actually Mean?

Without question, the Check Engine Light (also known as the Malfunction Indicator Lamp, MIL, Service Engine Light, or CEL), is the most common warning light drivers see when something is wrong with their car. Unfortunately, when the CEL comes on, it’s often accompanied by anxiety and stress. It’s easy to assume the worst when that yellow light comes on. 

If you’re in this position, don’t panic. Modern cars and trucks utilize a range of sensitive computers to monitor nearly every system while the engine is running. The check engine light alone isn’t always indicative of a catastrophic problem. In this article, we will look at some of the most common causes of a CEL and how to go about getting it fixed.

Common Causes of a Check Engine Light

As we said above, a check engine light is not always related to a serious issue. There are a few common things that can cause the light to come on, some of which you can fix yourself without getting your hands dirty!

Loose or Worn Out Gas Cap

Every element of the fueling system in your car, from the gas tank to the fuel injectors, is sealed to prevent the escape of environmentally harmful vapors. If you get gas and don’t fully screw in the cap, you will get a check engine light for evaporative emissions. Ensuring the cap is tight will eliminate the code.

If your car is older, the seal on the cap can wear out, leading to a check engine light. In this case, the cap will need replacement. 

Catalytic Converter Issues

The exhaust catalyst, or catalytic converter, reduces tailpipe emissions. This device sits in the exhaust, removing some of the harmful gasses produced by combustion and converting them to relatively harmless ones through a chemical reaction. 

A failing catalytic converter can cause a check engine light, reduced performance, and poor fuel economy. In Nevada, you won’t pass an emissions test with a failed converter. 

Spark Plugs and Ignition Coils

A faulty ignition system can cause the check engine light to come on. If the plugs are bad enough, you may experience a misfire, which happens when the air/fuel mixture in the cylinder is not ignited. Misfires will cause a flashing check engine light. If you see the light flash, stop driving your car immediately to prevent damage to the engine or catalytic converters.

Spark plugs are going to be a universal component across all gasoline engines, but the ignition system will vary from vehicle to vehicle, and will also depend on the age of your car. Older vehicles may use a coil pack, ignition coil, or distributor. If any part of the ignition system prevents the spark plug from firing properly, you will likely see a check engine light on the dash. 

Timing Problems

The bottom end of the engine (where the pistons and crankshaft live) and the cylinder head (which contains the camshafts and valvetrain) need to stay in perfect time with one another to run. Timing is achieved with a belt or chains, and these items will eventually wear out after tens (or hundreds) of thousands of miles of driving. 

Any discrepancy in timing can cause your check engine light to come on. An entirely failed timing system can lead to complete engine failure. Generally, if you have a timing problem, you will notice severe driveability issues in addition to the check engine light. 

Oxygen Sensor Problems

The oxygen sensor (also known as an O2 sensor) is a component that monitors the amount of oxygen in the exhaust gasses. These sensors tell the ECU how efficiently your vehicle is running, and whether or not the catalytic converters are working properly. Many vehicles will have an upstream O2 sensor (before the converter) and a downstream one (after the converter). If the sensor or the wiring connecting them to the ECU fails, you will get a check engine light.  

Getting a Check Engine Light Diagnosed

The aforementioned problems are just a sampling of some of the more common causes of a check engine light. Since the computer in your car is so sensitive, it’s virtually impossible to know what’s wrong based on the light alone.

Luckily, the computer in your car does a good job recording what exactly triggered the fault. Utilizing a code reader, your mechanic can narrow down the potential cause by pulling the fault. It’s important to remember that knowing the code isn’t always the end of the diagnosis. It can often take lots of additional time to track down where in the identified system something went wrong.

If you have a solid check engine light, it’s generally ok to drive the car to your mechanic. However, if the light is flashing, be sure to pull over and get a tow. It’s better to spend a little extra getting your car towed than risk causing more extensive -and expensive- damage. 

Check Engine Light Service and Diagnostics at Red Rock Repair

Are you a Summerlin or Las Vegas native with a check engine light? Don’t take a chance on your vehicle. Come into Red Rock Repair Las Vegas and let our experienced service team get to the bottom of the problem. Give us a call at (702) 385-7887 to schedule an appointment today!