What the Service Engine Soon Light Means + 9 Reasons

Your dashboard is displaying a service engine soon light, but there’s nothing unusual with your vehicle.

Wondering what this means and how to get rid of it?
We’ve got what you’re looking for!

Let’s discover nine possible reasons behind a service engine soon light and answer some frequently asked questions.

This Article Contains

What Does a Service Engine Soon Light Mean?
9 Reasons Your Service Engine Soon Light Activates
Are Service Engine Soon Light and Check Engine Light the Same?
3 Service Engine Soon Light FAQs

Let’s get started.

What Does a Service Engine Soon Light Mean?

The “Service Engine Soon” (SES) light indicates something is wrong with your car. It’s a sign of possible engine issues. The service light could mean a routine repair or maintenance, like a transmission service due. It could also indicate a serious problem like issues with your transmission, a vacuum leak, and increased emissions.

In either case, ignoring the ‘service engine soon’ light can cause problems to worsen, resulting in a complete vehicle shutdown and a massive hole in your wallet. You’re risking unnecessary expenses for extensive vehicle repairs, emergency roadside assistance, and towing fees.

Not sure when to take this light seriously?
Here’s how to understand what the light is trying to say:

A solid yellow or orange service engine soon’ light: If the warning light is yellow or orange, there’s a minor vehicle issue or service due. It’s best to check your vehicle before the problem becomes too severe.

A flashing or red ‘service engine soon’ light: A red warning light indicates a severe vehicle issue that requires immediate attention. If the service light pops up while driving, pull over immediately and tow your car to the nearest mechanic or call mobile mechanics, like AutoNation Mobile Service.

Now let’s figure out why the light even turns on in the first place.

9 Reasons Your Service Engine Soon Light Activates

Here are nine issues that could be behind your SES light:

1. A Faulty or Loose Gas Cap

This is usually one of the most apparent reasons behind a check engine soon light. A malfunctioning gas cap allows fuel vapors to leak. Leaking fuel vapors can trick your Engine Control Module into thinking there’s a problem. This minor issue can increase your vehicle emissions and fuel consumption.

What to do:
Tighten any loose caps or repair a faulty fuel cap.

2. Low Fluid Levels/Scheduled Service Overdue

Your service engine soon light could simply indicate that your car is past the scheduled oil change. It can also mean your engine oil levels are critically low.

What to do:
Check and replenish your oil or fluid levels as soon as possible.

3. Fuel Change

Needing a fuel change or gas refill could activate this light. The light could also point to a serious issue with your fuel system, like a faulty fuel pump.

What to do:
If you’re low on fuel, refill your gas tank. However, if your SES light doesn’t disappear, contact an auto repair professional and take your car for maintenance.

4. Faulty Oxygen Sensor (O2 Sensor)

Your oxygen sensor ensures a correct ratio of oxygen and gasoline in your vehicle. Your car won’t function properly if your gasoline-to-oxygen ratio is off.

Too little oxygen and too much gasoline can harm your engine. Likewise, too much oxygen causes poor engine performance and engine damage. If left untreated, a malfunctioning O2 sensor can also affect your spark plugs and catalytic converter.

What to do:
Take your car for routine maintenance and have the issue properly diagnosed and repaired.

5. Dirty Air Filters

Dirty air filters can damage your engine — leading to poor engine performance and affecting your driving. It might even allow harmful exhaust gases into your car’s cabin.

What to do:
Regularly clean your air filters — once a year or every 12,000 miles for a better driving experience.

6. Contaminated Gas

Contaminated gas can also trigger your ‘service engine’ soon light.

What to do:
Have your car work through 1-2 tanks of uncontaminated gas. If that doesn’t fix it, then visit an auto repair shop to confirm if there is a different error code.

7. Issues with Wires and Spark Plugs

Your car’s spark plug set and ignition cables are subject to wear and tear.

Worn plugs or wires could affect the combustion process, causing rough idle, difficulty accelerating, hard starts, or misfires. This could trigger the service engine soon light.

What to do:
Ensure your car undergoes regular maintenance and change your faulty spark plugs when it’s due.

8. Faulty Mass Airflow Sensor

The amount of fuel your engine needs depends on the amount of air that enters your engine. Your mass airflow sensor measures this air mass and sends a message to your vehicle’s computer indicating how much gasoline your engine requires.

So, a faulty mass airflow sensor can cause high fuel consumption and eventually cause your car to stall.

What to do:
Clean or replace your mass airflow sensor ASAP lest you want to inhale toxic exhaust gases or damage your spark plug system and your catalytic converter. Your bank account will take a massive hit if it comes to that. Have an auto technician run diagnostics and repair the possible P0101 trouble code.

9. Old Catalytic Converters

Expired catalytic converters can trigger a blinking SES light. The blinking won’t disappear unless the issue is sorted.

Plus, a bad catalytic converter can cause vehicle emissions to enter your car’s cabin, making driving risky and harming the environment with the increased emissions.

What to do:
Have your mechanic check and replace a worn-out catalytic converter.

People often confuse the cars check engine light and the ‘service engine’ soon light. So, let’s discuss their differences.

Are Service Engine Soon Light and Check Engine Light the Same?

Short answer — No.

However, some manufacturers use the terms ‘check engine’ and ‘service engine soon’ interchangeably. The best way to determine which warning indicator light (or idiot lights) your vehicle uses is to check your owner’s manual.

But here are a few differences to note:

The idiot lights present themselves differently. Your service engine soon light is spelled out as a word, whereas your check engine light could be an engine symbol or a ‘CHECK ENGINE’ text.

Your service engine soon light is a routine maintenance reminder. A check engine light alerts the driver to a potential problem with the engine or emission control system.

Have unanswered questions about the service engine soon light?
Keep reading!

3 Service Engine Soon Light FAQs

Here are the answers to two questions about the service engine light.

1. Can I Drive With a Service Engine Soon Light On?

Technically, yes, since your car won’t shut down immediately. But we suggest you get to a mechanic ASAP.

But if it comes on while driving and is blinking, please pull over and get it assessed by a professional auto technician.

2. How Does My Car Know It Needs Service?

Your vehicle’s Electronic Control Unit (ECU) or computerized engine controls does regular system checks, so any abnormalities trigger your warning lights. Your computerized engine controls work with your vehicle’s sensors to monitor all engine components.

However, certain vehicles have a predetermined service schedule that automatically triggers warning lights or codes on their dashboard to indicate an engine oil change or air filter replacement. These lights are activated once you’ve reached a specific gas mileage.

3. What Do Different Types of Check Engine Warning Lights Mean?

Much like your service engine light, your cars check engine light also lights up orange and red and can be solid or flashing.

Solid/yellow engine light: This could indicate a minor issue. You shouldn’t ignore it since it can cause severe damage if left untreated.

Blinking/red engine light: Needs immediate attention. It indicates a severe problem that can damage the engine if you keep driving, such as a misfire, a broken valve, or a blown head gasket. So seek out a mechanic ASAP.

Wrapping Up

If your dashboard lights up like a Christmas tree, it’s no time to be jolly. You need to diagnose and repair the issue behind the warning indicator light ASAP to avoid significant vehicle damage and a hefty mechanic bill.

Hopefully, our guide has enlightened you enough to deal with the service engine soon light appropriately. However, you should let professionals — like AutoNation Mobile Service, handle all maintenance and repairs, especially critical engine issues.

AutoNation Mobile Service’s mobile mechanics are available seven days a week to diagnose and repair your service engine soon light, right in your driveway.