Service Engine Soon Light: Meaning, Causes (How to Fix it)

You are driving along the road, suddenly, your dashboard lights up with the “Service Engine Soon” light. What should I do? Do I need to stop my car and have it towed to the garage? What is the cost of having it fixed?

These are a few questions you might have.

The “service engine soon light” isn’t as dangerous as you might think. This article is going to cover everything you need to know about the service engine soon light, what causes it, and how to reset the service engine soon light.

What Does Service Engine Soon Mean?

When your car’s onboard diagnostic system (the ECM) detects a problem, a Service Engine Soon light will be displayed. This light is designed to alert you to any potential problems before they become serious. You may need to change your oil or install a new cabin or air filter.

The intended function of the “service engine soon” light is to notify the operator that an emission system malfunction has been detected. It could be a serious problem with the engine or one of its components. However, it is usually minor.

Difference Between Service Engine Soon light And Check Engine Light?

Many people are confused about what the check engine light and the service engine soon lights mean. Although they may seem identical, we will show you how they are different.

Computers control a large part of your car, as with most things these days. The ECM (Electronic Control Module) manages everything under the hood.

The Service Engine Soon light illuminates when there is a minor electrical or engine problem. These could be a loose gas cap or low fluid levels, or an issue with the emission system.

If something isn’t working as it’s supposed to, such as a device running too slowly, too fast, too hot, or cold, the ECM relays this data and the Service Engine Soon light will be lit if certain conditions are met that could lead to your engine having problems.

The “Check Engine” light is usually a sign of greater concern. These include the need to replace the mass airflow sensor, a problem with the catalytic converter, or that not all cylinders are firing properly.

The Service Engine Soon light can be thought of as a mini-Check Engine light. They are so similar that some manufacturers combine them.

We’ll treat both as one since they both indicate that there is a problem and need your attention. Let us look at some of the most common reasons why a Check Engine or Service Engine soon light might be on.

What Causes Service Engine Soon Light

Service Engine Soon Light
Credits: Benjamin Clapp / Shutterstock

When there is a problem, the Check Engine or Service Engine Soon light will be lit. These can range from minor problems that are easy to fix to more serious issues that could be fatal to your engine. Let us look at some of the most common.

1. Routine Maintainance Alert

There are some things that need to be changed or checked up every now and again. After a certain amount of usage, time, or mileage, every car needs scheduled maintenance.

You might need to replace an air filter or change the engine oil. This is why the Service Engine Soon light was designed. This light is a reminder to have your engine checked by your local mechanic or dealer as soon as possible.

2. Spark Plugs Needs Changing

The condition of your car’s sparkplugs is another reason the Check Engine light or Service Engine Soon lights come on. The spark plugs ignite mixtures between compressed air and fuel in the combustion chamber. An explosion is created when the spark ignites, and then your car can move around with energy.

Spark plugs are designed to last for a long time and can continue working flawlessly for over 100,000 miles. They do have to be replaced periodically in order for the combustion process to function at its best.

3. Loose Or Faulty Fuel-Filter CAP (Fuel Cap, Or GAS CAP)

This is the most common reason your Service Engine Soon light may appear. ECU and ECM can detect if your fuel cap is missing or faulty. The fuel cap seals the fuel tank.

It can be used in both directions. It ensures that nothing can get in the fuel tank and contaminate it. It also helps to ensure that fuel, or fumes, do not leak out.

4. Low Amounts Of Fluid

There are many different moving parts in a vehicle. A car is equipped with many fluids to ensure that everything runs smoothly and protects against wear and tear. Fluids in a car include engine oil, coolant, and brake fluid. Transmission fluids are also included.

Low levels of these fluids could cause the Service Engine Soon Light (or other indicators) to flash. Low fluid levels can be either a sign that there is a leak or just a reminder to top up.

5. O2 Sensor Failure

it is essential for the engine to ensure that the air-fuel mixture of the internal combustion engine (ICE) powered cars remains optimal, as this is what gives the assurance that the engine is not only running smoothly and with sufficient performance but is also very efficient. This is always kept in check by the oxygen sensor (02 sensors).

This sensor monitors the oxygen levels in the engine and reports to the ECU. The O2 sensor can fail if the engine is burning too much (lean) or too little (rich). This can lead to poor performance, decreased fuel efficiency, and higher emissions.

A failure of the O2 sensor would cause the Check Engine light (normally) or service engine soon light to turn on.

6. Mass Airflow Sensor Failure

The Mass Air Flow sensor, or MAF sensor, works on the opposite end of the O2 sensor. It is equally important as it tells the ECU and ECM how much fuel to pump into an engine depending on the air intake. Variables like temperature and pressure can alter the air’s density.

It is therefore very important that the MAF sensor tells the engine how much fuel it requires. It should notify the engine if it is working properly to produce a clean, efficient burn.

The ECU could miscalculate how much fuel is being injected if the MAF fails. Not only would this cause damage to the engine, but it also results in the same problems caused by a faulty O2 sensor. This could lead to the service engine soon light or the check engine soon light coming on.

7. Catalytic Converter Failure

This is one of the most serious reasons that can cause the Check Engine or Service Engine Soon lights to go off. The atmosphere around you is affected by the release of toxic gases from burning fossil fuels like petrol and diesel. The problem is worsened by particulates that are released from the refinement of fuels.

Catalytic converters are found in most cars’ exhaust systems. Catalytic converters work to scrub off the harmful chemicals and pollutants that are released from the engine. Catalytic converters, although designed to last a long time, can wear out over time. This is especially true if your car continues to be driven for a long time with MAF and O2 sensors that are failing.

What To do if Your Service Engine Soon Light Comes On?

1. Identify Flashing/Solid/Color Of The Light

We mentioned that some cars have both a Service Engine Soon and a Check Engine light. Others only have one. It is often indicated by the intensity of the problem by how solid or flashing it is. Manufacturers may color code the indicator to indicate severity.

It’s usually a minor problem if it is yellow or solid, and this means that it can be fixed quickly. Flashing or red means that there is a serious problem. You should pull the car over as soon as possible and turn off the engine. To ensure safety, you should tow your car to a garage rather than driving it.

2. Pay A Mechanic To Diagnose The Issue

There are always people who are ready to take your money for car repairs. It usually involves setting up a drop-off time and giving them as long as half a day to complete the diagnostic. You can have either a friend or family member drop it off and pick up the vehicle or take an Uber both ways if you don’t own a second vehicle.

You should expect to pay up to $100, excluding the cost of a ride. You will know exactly why the light came on. If you are ready to allow them to repair any damage, some shops will waive the diagnostic fee. Trust is key. You don’t want to be overcharged for minor repairs.

3. Bring your car to an Auto Parts Store.

Although it may not be as detailed as taking it to a shop for repairs, you can still bring it to your local auto parts store. Many offer a free OBD II scan and will let you know the results. This is faster than taking it to a shop, and if it turns up to be insignificant, you may be able to fix it by yourself.

How To Reset Service Engine Soon Light

How To Reset Service Engine Soon Light
Credits: Melissa Brandes / Shutterstock

Let’s suppose you don’t want it to be sent to a dealership or workshop to be fixed. Even if your Service Engine Soon light has minor issues, labor costs can be quite high. There are plenty of things you can do at home that can be done quickly and easily if you have the time.

Here are certain ways you can fix service engine soon light

1. Tighten A Loose Fuel Cap

A loose fuel cap is one of the most common reasons why the Service Engine Soon Light comes on, so tightening it is a quick and easy way to reset the service engine soon light.

Turn off the engine and remove the fuel cap. Then, tighten it again. Perhaps you forgot to tighten it all the way when you last filled your car up. Start the engine and check if the Service Engine Soon light disappears.

Note, it might not immediately disappear and would require you to drive around for a bit before it does. The ECU might have detected that the fuel cap must be replaced if the light doesn’t go away. A replacement can be purchased quickly for $10-$20 from an auto parts store.

2. Check And Fill Your Car Fluids

This one can be easily checked and fixed while you are at home. Turn off the engine and inspect it for any leaks from the tanks. For assistance in finding them, consult the owner’s guide.

Then, check the engine oil, brake fluid, coolant, transmission fluid, and even the windscreen washers to make sure.

Each reservoir should be marked with the required minimum fluid level. If it is too low, then you can consult your owner’s manual again to see which brand of fluid is recommended. Pour in the required fluid and start your car to see if the service engine soon light goes away.

Note: Low fluid levels could also be a sign of more extensive problems, such as leaking or needing to completely change and flush some of the fluids.

3. Change The Spark Plugs

Changing a bad spark plug is another quick and easy fix for a service engine soon light. A faulty spark is one of the common reasons why the service engine soon light comes on. An changing a spark plug is something anyone can do.

Follow these steps to know how to change your spark plugs

  1. Make sure that your vehicle is turned off and the engine is cool.
  2. Remove the Spark Plug Wire.
  3. Remove the Coil On the spark plug.
  4. Unscrew the Spark Plug using a spark plug socket.
  5. Screw-in the New Spark Plugs.
  6. Re-install the Spark Plug Wires or coil.
  7. Start-Up the Engine.

Check out this video guide to know how to change your spark plugs

If after carrying out each of the following fixes the service engine soon light is still on, Take your car to an auto service center immediately to run a proper diagnostic test on your vehicle.

Frequently Asked Questions

What causes the service engine soon light to come on?

There are many reasons why your service engine soon light turns on. It could be a minor issue with your engine, low fluid levels, or minor emissions issues, depending on which car you have.

Can I drive with the service engine soon on?

As long as the service engine light is lit and it’s not flashing, you can drive safely. You should immediately pull over if the service engine light flashes and contact roadside assistance to have your vehicle taken to the mechanic.

How do I fix my service engine soon?

Turn off the engine, remove the fuel cap, and then tighten it. Perhaps you forgot to tighten the fuel cap all the way through your last car fill-up. Start the engine and check if the Service Engine Soon light disappears.

How urgent is the service engine soon light?

A solid service engine soon light indicates that you have an emission problem. A blinking service engine soon light indicates that you have an immediate problem and should immediately visit a garage.

Does service engine soon mean oil change?

When your car’s onboard diagnostic system (the ECM) detects a possible problem, a Service Engine Soon light will be displayed. This light is designed to warn you about minor problems before they become serious. You may need to change your oil or install a new cabin or air filter.

What is the difference between check engines or service engines soon?

The “Check Engine” light is a warning that something is wrong. It can indicate anything from a loose gas cap or a defective ignition coil. The “Service Engine Soon” light means that your vehicle needs to be serviced.

Will a service engine soon light fail inspection?

A vehicle’s onboard diagnostic system reports that there is a problem with an emission-related component or sensor. The “Check Engine” and “Service Engine Soon” lights may indicate that there is an issue. The vehicle will fail to pass the test if the light is on at the time you bring it in for inspection.

Conclusion

We hope you have learned some useful information about the Service Engine Soon light. You’ll hopefully be more prepared for the next Service Engine Soon light, should it ever appear in your instrument cluster.

The Service Engine Soon light is, in essence, a canary in the coal mine. If there is something wrong, it chirps. If you don’t pay attention for too long, you could be in for a lot of pain.

You might only need to replace a few sensors or a fuel cap. It may seem expensive, but paying more now can help you avoid costly repairs later. It is a reminder that you must always maintain your car’s health. It’s like practicing your own health care routine, exercising regularly, and eating a healthy diet.

You might not need to see the Service Engine Soon light if you take the same care of your car as you would with yourself. Be attentive to the smallest problems and oddities that may occur with your vehicle. You will not be let down by your automobile companion if you do this.

Scott Greene is a seasoned automotive technician for over 5 years and has been deep into advanced automotive diagnostics for a couple of years. He Loves writing about Automotive Diagnostics and Repair, Trouble codes, Buyer guides for various car parts and accessories, and lots more. 

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