Service Engine Soon Light: What It Means and How To Quickly Fix It

Service Engine Soon Light

Have you ever been driving along, minding your own business, when suddenly that dreaded amber “service engine soon” warning light pops up on your dashboard? It’s enough to give any driver a panic attack!

What does it mean when the service engine soon light comes on? Will your car break down if you keep driving it? And how can you make that annoying light turn off?

Relax! In most cases, it’s nothing to freak out about. Let’s break down everything you need to know about the service engine soon light, what causes it to come on, and how you can diagnose and fix the problem yourself.

What Exactly Does the “Service Engine Soon” Light Mean?

The service engine soon light, also known as the check engine light or malfunction indicator lamp, illuminates on your car’s instrument panel usually due to an issue with your vehicle’s emissions system.

It’s different than the oil warning light. The check engine light is triggered by your car’s on-board diagnostics computer (OBD) that monitors engine and emissions performance. The OBD computer runs self-tests of sensors, actuators, and vehicle components to make sure they are operating within the proper parameters.

When something is amiss – like an oxygen sensor misfiring or a loose gas cap – the computer turns on the service engine soon light to let you know there is an issue that needs attention. The idea is to alert you early on about a minor problem before it turns into a bigger issue.

Think of the service engine soon light as your car’s way of saying, “Hey, just wanted to let you know something’s not quite right under the hood. Schedule a check-up soon!”

The SES light simply means you need to schedule a service appointment, preferably soon, to avoid further damage and costly repairs. Diagnosing the problem early on can save you money and prevent more headaches down the road.

Okay, so the service engine soon light means you should get your car looked at, but it doesn’t necessarily mean you have to immediately pull over and call the mechanic. Let’s take a look at some of the most common culprits behind the dreaded check engine light.

5 Common Causes of the Service Engine Soon Light

1. Loose or Faulty Gas Cap

One of the most common causes for the check engine light to come on is a loose or faulty gas cap. Your fuel cap is a crucial part of your car’s evaporative emissions system and seals the fuel system from any outside contaminants.

Over time, the gas cap can become loose due to damage or just wear and tear. A loose fuel cap allows small evaporative losses from the fuel tank that the OBD computer will detect and flag.

The good news is this is one of the easiest issues to fix yourself. Simply check the gas cap to make sure it’s tightened properly and sealing correctly. If it is loose or damaged, replace it with a new fuel cap which you can find for cheap at any auto parts store. Replacing or tightening the gas cap takes seconds and can save you from an unnecessary trip to the mechanic.

2. Oxygen Sensor Malfunctioning

Another usual suspect for triggering the check engine light is a malfunctioning oxygen sensor. Your car’s oxygen sensors analyze the mix of oxygen and fuel leaving the combustion chambers and feeds that data to the engine computer.

If an oxygen sensor goes bad, it will send inaccurate readings that trick the computer into thinking there is an issue with the air to fuel ratio. Once the erroneous signals from the O2 sensor reach a certain threshold, the computer will turn on the check engine light.

Replacing a faulty O2 sensor is a common fix when dealing with an illuminated check engine light. While not a difficult DIY fix, it does require some mechanical know-how to locate and properly replace the bad sensor.

3. Catalytic Converter Problems

The catalytic converter plays a crucial role in reducing harmful pollutants from your engine’s exhaust emissions. It can become clogged or damaged over time from normal wear and tear.

A failing catalytic converter that is covered in carbon build-up or has deteriorated inside can cause problems with exhaust flow, throwing off the air-to-fuel ratio and triggering the check engine light. Replacing a bad catalytic converter will often solve the issue and turn off the warning light.

4. Spark Plug Issues

Sometimes the check engine light flickers on due to failing spark plugs that are causing ignition issues. Spark plugs provide the spark to ignite fuel in your engine’s cylinders. Over time, they become wore down and covered in carbon deposits, preventing them from firing properly.

Replacing worn out or fouled spark plugs can readily fix the problem. While spark plugs eventually need replacement in any car with high mileage, an engine misfire from faulty plugs can cause the check engine light to come on signaling the need for a tune-up.

5. Vacuum Leak

Any vacuum leaks in the hoses, tubes, or gaskets that meter air on the intake side can also cause the check engine light to illuminate. Small leaks allow extra air to mix with the fuel, throwing off the precise air-to-fuel ratios that the computer is expecting.

Carefully inspect all vacuum line connections, intake gaskets, and hoses for signs of cracks or damage. Replace any degraded tubes or gaskets that are causing air leaks in the system. This cheap fix can solve the underlying problem and turn off the SES light.

How to Diagnose What’s Causing the Check Engine Light?

Alright, so you’ve realized the service engine soon light is not just a fluke and needs to be looked at. How do you figure out what’s causing it to come on?

First, you’ll want to read the diagnostic trouble codes (DTCs) stored by the computer that is triggering the malfunction indicator light. You can have these codes read for free at most auto parts stores. Another option is to use an OBD-II scanner tool to read codes yourself and get a head start on diagnosing the issue.

OBD scan tools plug into your vehicle’s port – usually under the dash – and display any codes being thrown that are illuminating the check engine light. For example, the code may show an oxygen sensor or catalytic converter problem. The DTCs provide insight into which component or system is malfunctioning, allowing you to pinpoint the root issue.

From there, you can better determine whether it’s something simple you can fix yourself (like a loose gas cap) or if the car requires shop repair.

Resetting the Service Engine Soon Light

Once you’ve diagnosed and fixed the problem triggering the check engine light, you’ll want to reset the light. Begin by double checking the light was due to a faulty spark plug, oxygen sensor, or other component you replaced and that the underlying problem is fully resolved.

Here are a few common ways to reset the pesky check engine light:

  • Use an OBD-II Scanner Tool – The quickest way is to use an OBD2 scanner to clear any DTC error codes that are illuminating the light. Most auto parts shops can plug in a scanner and reset the computer for you when doing the repair.
  • Disconnect the Battery – With the vehicle off, disconnect the negative battery cable for 30 seconds to reset the computer and turn off the service engine soon light.
  • Drive It – Driving with the check engine light on is not harmful to your car. The OBD computer will reset itself after a certain number of drive cycles (usually 75-100 miles). The SES light will turn off on its own if the error was temporary and fixed itself.
  • Time – In some cases, all you need is time. If the light was due to a minor engine hiccup that worked itself out, the OBD computer will automatically reset after a couple days and turn off the service engine soon lamp.

When Should You Take Your Car to a Mechanic?

While the check engine light does not mean you have to immediately pull the car over, you do need to get the underlying problem inspected and fixed as soon as it’s convenient. Give it a couple days to reset on its own if it was a temporary glitch.

Simple issues like a loose gas cap are easy and cheap DIY fixes. For more complex problems beyond your skill level, take your car into a professional technician for diagnostic and repair.

A reputable mechanic can read the OBD trouble codes, run tests, and accurately determine why the check engine light keeps coming on. It gives you peace of mind knowing your car is fixed properly.

Here are signs it may be time to take your vehicle in for service:

  • The service engine soon light stays on after attempting DIY fixes
  • You notice engine performance issues like loss of power when accelerating
  • Multiple check engine lights have illuminated indicating various problems
  • The warning light is flashing or blinking (typically signals severe issue)
  • You smell gasoline fumes coming from your vehicle

While the service engine soon light can seem ominous, in many cases it’s as simple as replacing a 25 cent gas cap. But it’s still smart to have it properly diagnosed so you can catch any major problems early and make repairs before lasting damage is done.

With a little DIY troubleshooting, you can learn to diagnose the check engine light yourself. But when in doubt, call your local ase certified mechanic to inspect and reset that annoying service engine soon light for you!

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