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How To Diagnose Check Engine Light

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The Check Engine Light always generates an uneasy feeling when it silently starts to glow on a dashboard. Read on to learn more about the significance of why the Check Engine Light comes on and learn more about how you can start to diagnose some of the issues. It is important to realize the Check Engine Light is there to warn you of an issue with your vehicle and should not be ignored.

Popular Reasons The Check Engine Light Comes On.

Gas Cap Issues.

Your gas cap prevents vapors emitted from the gas tank from escaping into the atmosphere. As the gas cap is vital to the EVAP Emission Control System the cap and the lines, fitting and connectors can all leak, but the gas cap is most likely to be the cause. This can cause fuel to evaporate, and the recirculation system will not work to its upmost capabilities.

Oxygen Sensor Issues.

Essentially the oxygen sensor calibrates unburned oxygen in the exhaust of your vehicle and measure the fuel and air mixture while the engine is combusting. Often with a life span of around 80,000 miles, it can generate many engine codes when it is not working but is not indicative that the oxygen sensor is at fault. However, if the oxygen sensor needs replacing and you delay doing it, you will burn more fuel than needed and damage can be caused to the catalytic converter and spark plugs.

Misfiring Engine.

It is vital spark plugs fire up the fuel and air mixture in the combustion chamber of a motor vehicle. If the sparks are not igniting at the right time, it can cause single or multiple engine misfires. Changing the coils over from one cylinder to another can help to identify if it is a spark plug issue. Although tougher to diagnose, the engine misfiring may also be caused by a defective fuel injector or a vacuum leak. Sometimes, spark plugs and the wires associated with them can just wear through age, especially with older vehicles. More serious issues may be piston rings that have become worn and can be diagnosed with a compression test of the engine. Ultimately misfiring causes mechanical engine failure though early signs may be reduced power and fuel economy.

Issues With The Mass Airflow Sensor.

A Mass Airflow Sensor determines the amount of fuel versus the amount of air needed to make the engine work correctly. The sensors can pick up dirt, water vapor and oil and can cause the Check Engine Light to come on. Conversely, there are times when the sensor needs to be replaced. As a result, you will notice reduced fuel economy and performance issues.

Catalytic Converters.

Usually, catalytic converters will not just stop working but is caused by other components not working correctly. Therefore, replacing the catalytic converter does not often remedy the issue. It can be indicative of a blown head gasket and if nothing is done not only will your vehicle fail emissions test it will not perform as expected and may be the cause of engine failure.

Diagnosing Issues.

Minor problems like a loose gas cap or a faulty oxygen sensor can often be addressed as a simple DIY project but more serious issues like a failed catalytic converter or other complex problems may lead to mistakes if you try to repair them yourself and it is highly advised at that point to get a professional mechanic involved.

When Ignorance Is Not Bliss.

If you choose to ignore the check engine light many things can happen and none of them are good! As well as a decrease in performance and feel efficiency, your vehicle can put out increases in emissions and you may take a minor problem and without addressing it, it becomes a major problem. It can also lead to safety concerns.


Some of this can be addressed by adhering to regular scheduled maintenance on your vehicle, making sure the gas cap is always tightened, disciplined and responsible driving techniques and using quality fuel.

The team at Heath’s Auto Service in Prescott, AZ would be happy to help with all of your automotive service needs!

At Heath’s Auto Service, we take pride in being your one-stop destination for full-service auto and truck repair in Prescott, AZ. Our team of skilled technicians possesses a wealth of experience and knowledge, allowing us to confidently handle domestic, Asian, and European vehicles with precision and expertise. Contact our team today!


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