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What Does The Service Engine Soon Light In My Car Mean?


What Does The Service Engine Soon Light In My Car Mean?

Cars and trucks have plenty of helpful warning lights on the dashboard. But, unfortunately, it’s not always clear what each of them means. One perfect example is the Service Engine Soon light. While the instructions might be clear, the reasons behind that light illuminating or flashing aren’t easy to understand.

The precise meaning of the Service Engine Soon light can differ depending on your vehicle’s make and model. Generally, the light comes on because there are minor engine issues or because the car is due for its regular maintenance. It’s also possible that the engine is running low on fluids or experiencing minor exhaust emissions problems.

In this guide, you’re going to learn everything you need to know about the Service Engine Soon light and why it might be coming on for your car. We’ll begin by exploring what the Service Engine Soon light is and what it means. Then, we’ll look at the most common reasons it comes on and what you should do when it comes on.

What Is The Service Engine Soon Light?

The Service Engine Soon light is a way for your car to warn you that there might be a minor problem with the engine. The light comes on as a gentle reminder to take your car in for its regular maintenance to address minor issues before they become major problems down the line.

Depending on your vehicle make and model, the Service Engine Soon light might look slightly different in terms of color and design. Plus, the way the light blinks or stays on to indicate the severity of the problem might also be different depending on the manufacturer.

Example of a service engine soon light on a GMC car

One thing is for sure: no matter what type of car you drive, you should bring it to your trusted workshop as soon as possible when the Service Engine Soon light comes on.

Check Engine Light Vs Service Engine Soon Light

In simple terms, a service engine soon light indicates that there is something minor wrong, like a maintenance, oil change, air filter change, etc. While a check engine light indicates there is something wrong that needs your immediate attention.

Some car manufactures though, use it as a way to sell you more services. If that’s the case, a service engine soon light could indicate that there is nothing wrong with the vehicle, but you should come to the dealer so they can sell you an oil change, air filter, inspection, or something else.

What Causes The Service Engine Soon Light To Come On?

The component inside your car which turns on the Service Engine Soon light is known as the ECU or Engine Control Unit. Sometimes, you may find that this is instead referred to as the Electronic Control Module (ECM) in your car owner’s manual.

Essentially, what happens is that the ECU and its sensors detect a problem with the engine and warn you about it by turning on the Service Engine Soon light. Unfortunately, these components can’t give you a definitive answer as to what’s wrong. They can only give you a rough indication that the problem is located in the engine.

If you’d like to know what that light means precisely for your car, your best guide would be the user manual. 

Still, here are a few typical reasons why the ECU would turn on the Service Engine Soon light in most cases.

1. Minor Engine Issues

The Service Engine Soon light could come on for even the most minor of reasons. For instance, the light might turn on in some cars even if one of the fluid caps is loose and requires tightening.

These issues are pretty straightforward to resolve. All you’ll have to do is pop the hood and look for anything that’s out of place. Alternatively, you could also check the user manual for any instructions on the essential items that need to be checked.

Don’t let the name fool you. Just because it’s a ‘minor’ engine issue doesn’t mean you should ignore it. On the contrary, it’s always best to have the issue resolved while it’s small, as it’ll take more time, effort, and money to fix it if it ever becomes a big problem.

2. Overdue For Routine Maintenance

Some vehicles might also be able to sense how long it’s been since your last routine maintenance. If that’s the case, the Service Engine Soon light might also come on as a gentle reminder that you’re due for another maintenance session shortly.

Typical vehicle maintenance will include an oil change, topping up of fluids (like coolant, brake fluid and transmission fluid). Besides that, it usually includes a multi-point inspection where the mechanic checks to make sure your vehicle is in good working order.

To be sure, check your vehicle’s maintenance records to see how long ago the last maintenance session took place and when the next one is due.

3. Low On Fluids

The Service Engine Soon light could also be an indicator that your vehicle is low on fluids. Some examples of fluids that might be running low include:

  • Engine oil.
  • Coolant.
  • Brake fluid.
  • Transmission fluid.

4. Potential Leaks

Suppose your vehicle is low on fluids. If that’s the case, then the Service Engine Soon light could indirectly be warning you that you have a leak somewhere in your engine.

Yes, it’s absolutely normal for auto fluids to run low after a certain amount of time. However, fluids running low faster than expected, primarily if you’ve just performed routine maintenance on the vehicle, could be indicators that there’s a leaking hose or gasket.

This is the kind of problem you don’t want to delay fixing, so be sure to get it checked as soon as possible!

5. Problems With The Vehicle’s Emissions

Newer vehicle models are also equipped with sensors monitoring the car’s exhaust emissions. So even though those emissions come out through the exhaust, you can typically trace their problems all the way back to the engine.

There’s also a possibility that the Service Engine Soon light might be coming on because of a minor exhaust emissions problem. For example, the ECU might be sensing that there’s too much smoke coming through the exhaust system or that there might be a leak somewhere along the way.

When the vehicle’s sensors detect these minor exhaust issues, the ECU will try to alert you by illuminating or even flashing the Service Engine Soon light. 

Related: How To Tell If a Catalytic Converter Is Clogged

What To Do If The Service Engine Soon Light Comes On

Some people might start to get worried when they see the Service Engine Soon light appear on their dashboard. If that sounds like you, try not to worry too much. The light is simply telling you that there’s an issue that requires your attention.

If you find yourself in this position, you can begin by performing some basic checks on your vehicle. Then, you can dive in deeper by performing diagnostics on the car or taking it to your preferred mechanic for a more thorough inspection.

Basic Checks:

This has already been said repeatedly, but it’s worth mentioning once more: always check your car owner’s manual first whenever the Service Engine Soon light comes on. That’s because the manufacturer would have detailed instructions on what’s causing the light to come on and what basic checks you should perform.

Still, here are a few parts that you can check as part of your troubleshooting process:

1. Fluids

First and foremost, check your vehicle’s fluid levels. That includes the engine oil, brake fluid, transmission fluid, and anything else that you suspect might be running low.

While you’re at it, keep a lookout for any possible leaks around the gaskets or seals that could be causing any of those fluids to run too low.

2. Caps

Next, check that all of the caps are closed tightly. Remember: on some vehicles, the Service Engine Soon light could be triggered by a loose cap for the oil reservoir or any other fluid.

Note: Be careful when you’re touching the radiator cap, and never open it, especially when it’s hot. When the car and radiator are still hot, the pressure is incredibly high in the radiator. You could hurt your hand grabbing the cap, and you might send hot water spray out if you were to open it.

3. Noises

As you check your car, try to pay attention to any unusual noises that you might sense. That includes both when the car is off and when you turn it on.

For example, some leaks are hard to identify visually. Instead, you may hear a hissing noise that helps you locate the source of a leak, such as on one of the hoses on or around the engine.

Those leaks could lead to a loss of fluids which would trigger the Service Engine Soon light.

Routine Maintenance Schedule

Lastly, be sure to check your routine maintenance schedule. It’s very easy for people to forget when their cars are due for their following oil change. However, you might discover that the next session is due soon, which might be why the Service Engine Soon light came on in the first place.

In some cases, the date of your next routine maintenance session might be written on a sticker attached to your windshield by the mechanic during the previous routine maintenance.


Besides performing regular checks on your vehicle, you can also take it a step further by performing diagnostics. Most recent car makes and models have onboard diagnostics (OBD), and you can purchase an OBD scanner or reader that plugs into that system.

With an OBD scanner or reader, you’ll be able to read the unique error codes generated by your car. Those error codes will give you a better idea of what problem(s) are causing the Service Engine Soon light to come on.

Having that information is incredibly helpful when you go to the mechanic because you’ll be able to tell them what error codes show up. That will save them a lot of precious time troubleshooting the issue. They can get started on resolving the issue immediately.

Alternatively, it could also save you a trip to the mechanic if you find that the problem can be fixed right in the comfort of your own home.


Of course, the most straightforward solution to the Service Engine Soon light is to take the vehicle to your preferred mechanic. Once there, the mechanic could inspect the vehicle themselves and use their equipment to run thorough diagnostics on your vehicle.

Frequently Asked Questions (FAQ)

Here are answers to some of the most frequently asked questions about the Service Engine Soon light.

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