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Top Reasons Why Your Check Engine Light Is On

July 5, 2021

When your vehicle’s onboard computer detects trouble, it will trigger a check engine light. Don’t wait to take your vehicle to a mechanic for diagnostic testing. Ignoring the issue could lead to an unexpected breakdown. Here are the most common auto repair problems that cause the check engine light to come on.

Loose Fuel Cap

Hundreds of drivers make the mistake of forgetting to tighten their gas cap. Upon detecting a loss of pressure in the fuel tank, the car’s ECU will immediately set off the check engine light. Luckily, this is an easy problem to fix.

While a loose or missing gas cap want won’t affect your vehicle’s performance, it can cause you to waste fuel. Over time, this problem can also allow moisture to collect inside the fuel tank. Furthermore, you should consider the environmental impact. The escaping gasoline vapors definitely contribute to air pollution.

Bad Catalytic Converter

The Environmental Protection Agency requires all modern vehicles to be equipped with a catalytic converter. This component, which is part of your car’s exhaust system, is engineered to convert toxic emissions into harmless gas. While catalytic converters can last the life of your car, they often go bad sooner than expected. Poor vehicle maintenance is often the cause of premature failure. Motor oil and antifreeze leaks can be especially damaging.

Aside from triggering the check engine light, a bad catalytic converter can also produce a rotten-egg smell. If the honeycomb material inside the converter breaks apart, this can clog the exhaust system. Expect to experience a major loss of performance. Because of the engine's reduced output, your car will feel extremely weak when climbing hills and merging onto the highway.

Worn Spark Plugs

It’s important to have your spark plugs replaced at the recommended intervals. Bad spark plugs can dramatically impact the drivability of your vehicle. Rough idling, hard starting, and sluggish acceleration can all indicate the need for a tune-up.

Severely worn spark plugs will eventually set a trouble code, thus causing the check engine light to turn on. If you notice your check engine light flashing repeatedly, pull over as soon as possible. You’re dealing with a severe misfire. Continuing to drive your car can lead to major engine damage.

Bad Oxygen Sensor

Most vehicles feature at least two oxygen sensors. While a bad downstream oxygen sensor will trigger a check engine light, failed upstream oxygen sensors can cause your vehicle to run poorly. Reduced fuel economy is another potential outcome.

To determine if your oxygen sensors are in good condition, a mechanic will need to use a diagnostic code reader. Generally, most of these sensors last between 50,000 and 60,000 miles.

Failing Mass Air Flow Sensor

Your vehicle’s mass air flow sensor helps the engine to maintain an optimal air-fuel ratio. When a mass air flow sensor begins to fail, you may not initially notice any problems. However, it’s only a matter of time before things worsen. Among the potential issues power loss, reduced gas mileage, and hesitation.

The best way to protect your mass air flow sensor is to regularly change the engine air filter. Ideally, you should install a new filter every 15,000 miles. This helps to prevent dirt and other contaminants from getting onto the part’s sensitive filament.

If your service engine light is illuminated and you are in need of expert auto repair service, come see us at Creech Import. We treat all our customers like family. Our ASE certified mechanics work hard to get your vehicle running and performing at its best.