What Does the Service Engine Soon Light Mean & How to Fix

When the Service Engine Soon Light suddenly appears on your dashboard, it can understandably cause you to worry. After all, dashboard indicator lights are intended to warn us that there is a problem.

But, what does this service engine soon light mean? And what problems is it warning us about?

Service Engine Vs. Check Engine Light

One issue with understanding what the Service Engine Soon light means is that it is often used interchangeably with the Check Engine light. This happens when a vehicle has one or the other indicator light, but not both. For instance, if you have a Nissan, the “Service Engine Soon” and “Check Engine” light mean the same thing. If this is the case, then they both have the same meaning.

Some car models, however, have both a “Service Engine Soon” and a “Check Engine” light. If this is the case, they have different meanings and indicate different problems.

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What Does Service Engine Soon light Mean?

Here are some of the common issues the service engine light may be warning you about:

This is one of the most common causes of the service engine indicator light to go on. Thankfully, it is also easy to check for the problem and fix it yourself.

Open the gas cap door so you can check the cap. First, inspect it for damage. Look for signs such as chips, tears or cracks. If you see any of these, simply change the gas cap to resolve the issue.

If there is no damage, just re-install the cap in the filler tube. Turn it to tighten until you hear a click to indicate it is in place. If it does not click or still feels loose, you may need to replace it.

After replacing the cap, drive around for a while. If you’ve replaced the cap properly, the light should go off. If it continues to appear, check the cap again.

2. Spark plug issues

Spark plugs are an essential part of the combustion process in your engine. They create electrical sparks that ignite the gasoline in the engine's combustion chamber. To be able to do this, they need to get sufficient power from the ignition coils.

There are a number of problems that can cause spark plug issues, including worn-out spark plugs, ignition coils not working properly, loose connections and incorrect installation. If any of these happen, you will see the Service Engine indicator light.

You can avoid these problems by changing the spark plugs according to the recommended schedule in the owner’s manual. You can also ensure that your car has regular tune-ups and maintenance work done. But if these issues continue to persist, you should have your car looked at.

3. Malfunctioning oxygen sensor

Oxygen sensors monitor the levels of oxygen in the gas that is leaving the engine. It then produces a voltage based on whether there is too much or too little fuel in the mixture.

This computer uses these voltage levels to adjust the mixture of lean (insufficient fuel) to rich (excess fuel) by adjusting how much fuel is going into the engine. This ensures that the gas-oxygen mixture is constantly moving between these two extremes so that your engine will be performing well.

If the O2 sensor is not working properly, it can cause the oxygen-gas mixture to become too oxygen-rich. Eventually, your vehicle will start producing too much dirty exhaust that smells like rotten eggs. If the problem is not addressed, it can hurt your car’s fuel efficiency and eventually, damage your catalytic converter.

You have to get your car checked to see if there is something wrong with the oxygen sensor, or if there is an underlying problem that is causing false readings. Changing your sensor without addressing these issues will only cause the Service Engine Soon light to eventually reappear.

Also Read: trick o2 sensors

4. Faulty Mass Airflow Sensor

In order for the engine to work properly, air and gas should be taken into it in particular proportions. The mass airflow sensor measures how much air goes into the engine. This information is used by the Engine Control Unit to adjust how much fuel should be delivered to ensure the optimum ratio of gas to air.

Aside from the Service Engine indicator going on, other symptoms of a  mass faulty air flow sensor include difficulty in starting or turning over the engine; after starting, the engine stalls; a hiccuping engine; while accelerating, there is jerking and hesitation; and while idling or under load, the engine drags or hesitates.

The best way to avoid this issue is to clean your sensor regularly. You can do this by carefully removing the sensor, making sure to avoid touching the wires, since these are delicate and can easily be damaged.

You can place the sensor in a bag filled with rubbing alcohol. Swish it around to ensure that all the dirt and grime is removed.

Alternatively, you can buy a cleaning solution specially designed for mass airflow sensors. Then simply use as directed on the label.

Whichever cleaning method you choose, let it sit for at least twenty minutes or until it is completely dry. Then you can reinstall it. If the indicator light continues to go on, you may need to have your car looked at by a mechanic since the sensor may be damaged or there may be other problems.

Investing in a Code Scanner

If you feel like you can perform your own minor maintenance tasks, you might want to invest in an OBD-II scanner. The scanner will provide the diagnostic codes that identify what the problem is that is causing your Service Engine indicator light to keep turning on.


You should not ignore the Service Engine Soon light Meaning when it suddenly turns on. It is your car’s way of warning you that there is an issue that you need to fix as soon as possible. You can either take your car to the shop or look at it yourself if you are handy with automobiles. But make sure that you address the problem before it can become more serious.

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