That pesky Check Engine Light that occasionally illuminates on your dashboard is the first indicator that something may not be right. It is incredibly annoying and tends to appear at the worst possible time, but ignoring it can cause bigger issues down the road (literally). There are numerous reasons that can trigger the check engine light ranging from a loose fuel cap to a problem with the ignition.

To help ease the stress, we have compiled a list of common reasons as to why your check-engine light may come on.


A loose fuel cap is one of the most common reasons as to why your check-engine light will turn on. The fuel cap is essential to sealing the fuel system and maintaining pressure within the fuel tank. It also prevents gas fumes from leaving the fuel tank and keeps the whole system under the correct pressure.

If you get gas and your check engine light turns on right away, pull over and make sure it is fastened all the way – or not on top of your car. Then make sure you turn your car all the way off and then back on to double-check if the light is still on. If you have a loose fuel cap, it is an inexpensive replacement that won’t break the bank to replace.


Worn or fouled spark plugs can cause a variety of issues for your vehicle, like an engine misfire or reduced power. Spark plugs ignite the air/fuel mix in the combustion chamber. The spark plug wires deliver sparks from the ignition coil to the spark plugs, making it a very important part of your vehicle.

If the spark plugs and wires are worn out or fouled, they could cause your car to shut off unexpectedly, have rough idle, have a poor engine performance or low gas mileage. Worn plugs can also cause clogged catalytic converts or damage to your ignition coils and O2 sensors.


Oxygen sensors measure the amount of unburnt oxygen in your vehicle’s exhaust system. This is an essential part of the ignition because it sends data to the vehicle’s computer so that it can regulate the mixture of air and fuel that enters the cylinders.

Your engine will continue to run if the oxygen sensor needs to be replaced, but it will burn an excessive amount of fuel in the meantime. If you leave a bad oxygen sensor for too long, it can start to damage other parts of the vehicle like the spark plugs or catalytic converters.


A catalytic converter is a part of your vehicle’s exhaust system that turns the carbon monoxide generated during the combustion process into carbon dioxide. This part is very preventable from failure with regular maintenance checkups and oil changes. Making sure you keep the catalytic converter maintained is very important because a new one can cost anywhere between $200 and $600. Also, keep your eyes and ears peeled for any unusual sounds or discolored smoke coming from your exhaust.


The exhaust gas recirculation valve in your vehicle lowers the amount of nitrogen oxide that comes from the engine of your vehicle to make it run in a more efficient way. It helps warm up your vehicle’s fuel by directing the exhaust gases back into the combustion chamber. This will help burn fuel easier and will also help reduce emissions.

The exhaust gas recirculation valve can easily get clogged up or fail, causing a need to replace it or have it cleaned out. The valve cost around $125 to be replaced by a brand new one.


The airflow sensor monitors how much air enters the engine of your vehicle. The airflow sensor is a part of the engine management system, meaning your vehicle would not be able to adjust to changes in altitude without it.

Some symptoms of an airflow sensor failure include a rough idle, trouble starting and sudden changes in the position of the throttle pedal. Reduced gas mileage and stalling of your vehicle may also indicate that you have an airflow sensor problem.


A vacuum system performs a handful of tasks in your vehicle, like lowering harmful emissions by routing fumes of gasoline that evaporate through the engine. If your vehicles idle starts to surge or settle at a high rpm, a vacuum leak may be the reason behind it.

As vacuum hoses age, they can begin to dry out and crack, especially during extreme temperatures. Intense heat or intense cold in the most common cause of a vacuum leak. A vacuum is fairly cheap to replace but can end up being expensive while trying to find the source of the leak.


If an aftermarket alarm is not properly installed in your vehicle, it can cause massive issues. It could drain your vehicle’s battery, trigger your check engine light or prevent your vehicle from starting. It could also cause your alarm to be triggered by the smallest things, like a leaf falling on your vehicle in the middle of the night.

If you are experiencing any of these vehicle symptoms, you will need to have the alarmed fixed, reinstalled or entirely replaced by a mechanic. Getting it fixed right away will be helpful in the long run. Leaving the malfunctioning alarm in your vehicle for too long could cause more issues down the road.

Whether it is a vacuum leak or a failed oxygen sensor, a check engine light is never a good sign. When your check engine light comes on, trust All Tune & Lube to help solve your problem.

941 Blairs Ferry Rd NE Cedar Rapids, IA, 52402 (319) 550-3390
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