Service Engine Soon Light : Explained and How to Fix (Answer)

Service Engine Soon Light

Technology has become a key component in modern automobiles. Most vehicles use onboard computers in tracking the performance of individual engine parts. In case of the occurrence of any problem occurring, the computer records it as an error code.

One of the problems that such a computer can detect is the service engine soon light. This article discusses what it means, causes, and how to fix it.

What Does Service Engine Soon Light Mean?

When this light appears, it could be a warning to you that the sensors in your vehicle have identified a problem.

In most cases, it could signal a minor problem with the engine of your car. Also, it could be a sign that there is an issue with the electronics in your vehicle.

For some other makes, it could be a signal that you need to do some scheduled service. Such services could be like oil replacement. It could also mean that you need to replace your spark plug.

If your car make is a Nissan, the service engine soon light can be a sign of a loose gas cap. It can also signal a significant problem, such as the likelihood of an engine failure.

Curious to know how long gasoline last? – Read this

Why You Shouldn’t Ignore this Light

Although this could just be a warning, it is wise not to ignore it. In most cases, the service engine soon light alerts you of a minor issue before it can become more prominent.

You may not necessarily have to pull off the road and take your car to the garage when you see this light. However, it is crucial to schedule an appointment to have it fixed.

The reason you should ignore this warning is that it could graduate into a bigger problem if not fixed. In case it becomes bigger, it could result in serious damage to car components. Fixing this later could end up costing you a lot more.

Common Reasons for the Service Engine Soon Light

1. A Loose or Faulty Gas Cap

Yes, this is among the issues that can cause the Service Engine Soon light to come on.Fortunately, it is a simple and quite inexpensive fix. It is an issue you can eve fix it yourself.

2. Faulty Oxygen Sensor

The ratio of oxygen to gasoline in your car is very crucial. It is a requirement for your car to operate optimally.

Too little oxygen is harmful to your engine. It causes it to run “rich” from the gasoline that remains after the combustion process.

On the other hand, too much oxygen is also not good for your engine. It will, in most cases, lead to poor engine performance. In extreme cases, it can even cause damage to the engine.

It is for this reason that your engine sensor is critical. Together with the engine computer, the sensor determines and adjusts the ratio of air to gasoline.With a faulty sensor, the computer fails to adjust the air to gasoline ratio.

This failure by the computer causes the lights to come on. If not checked early, a malfunctioning sensor can lead to loss of engine power. In later stages, it may eventually affect your spark plugs and catalytic converter.

3. Spark Plugs & Wires

Bad Spark Plugs

The spark plugs and wires often wear out with time. Consequently, they require replacement after some time.

If your plugs and wires are faulty, they may affect the combustion process.You can easily notice plugs that are misfiring. As you accelerate, you will feel a little jolt.

4. Mass Airflow Sensor is Faulty

The mass airflow sensor is critical in a car. Its main work is to measure the volume of air going through the air filter.

After measuring, it communicates to the computer how much fuel the engine requires. The amount of air entering the engine determines the amount of fuel.

A faulty mass airflow sensor will result in poor gas mileage.Your vehicle may also start to stall.

Delayed replacement of the mass airflow sensor can also be very risky. It can damage the spark plugs and the oxygen sensor. It can also cause damage to the catalytic converter.

How to Fix the Issues and What to Do

1. A Loose or Faulty Gas Cap

To begin with, take the gas cap off and put it back. Drive the vehicle for a few minutes. The Onboard Diagnostic (OBD) system should be able to reset and turn the light off.

However, if after a few drives the lights are still on, you may have to replace the gas cap.You will need to get a cap that is for the exact make of your vehicle.

Once done, drive the vehicle again for a few times. This drive is to allow the ODB system to reset.

If, after all these, the lights are still on, you may have to visit a garage. You can then get a proper diagnosis of what the real issue could be.

2. Spark Plugs & Wires

For spark plugs and wires, you need not wait until they completely wear out. Check your vehicle manufacturer’s schedule and replace them accordingly.

You can do this at home all by yourself. All you require are a few simple tools, which include:

  • Screwdrivers
  • Ratchet and sockets
  • Wrench set
  • Spark-plug wire pliers, if needed
  • Goggles, if needed
  • A new set of spark plug wires for your car model
  • Needle-nose pliers, if needed
  • Floor jack, jack stands or wooden blocks

How to Change the Spark Plug Wires

The best way is to start at one end of the engine then work towards the other end. Replace one spark plug wire at a time to avoid connecting a wire to the wrong cylinder.

  • Ensure you wait until the engine has cooled to avoid getting skin burns.
  • To have easy access to the plug wire, you can move to the side any part that may block you. Some of such parts include the air cleaner duct, engine cover, or radiator fan shroud. You will only need a screwdriver to do this.
  • From one end of the engine, choose one spark plug wire. Hold the wire boot with your hand and twist it from side to side, as you pull it. A spark-plug wire plier may help you reach the boot if you can’t reach it with your hands.
  • If some clips have hooked the wire into its place, unhook it.
  • Check the other end of the wire and disconnect it from the distributor or ignition coil. You may need to use a pair of needle-nose pliers in case a spring clip has secured the boot to the distributor.

Faulty Mass Airflow Sensor

  1. Locate the MAF sensor on the air cleaner assembly after opening the hood of your vehicle. You will find it between the air filter housing and the throttle body. However, in some other models, you will find the MAF sensor in the filter housing.
  2. Check the air duck for an electrical connector. You will find the air duct after the air filter housing. In case you do not seem to find it, you can consult your repair manual.
  3. Plug the electrical connector into the sensor. See whether you can back probe the wires. In case it is not possible, pierce the wires with a pin as you conduct your tests.

Note that if you have pierced the wires, you may need to wrap them with electrical tape. The wrapping helps to ensure they do not rust later.

  • On the electrical connector, look for the power, ground(s), and signal wires. You can get this information on your repair manual, or you can search online.


In conclusion, it is risky not to fix any issue that causes Service Engine Soon light to come on.Such issues can lead to the failure of the catalytic converter. Fixing a catalytic converter can be very expensive.

Consequently, ensure you maintain your vehicle. Do not ignore any small problem, but ensure you fix it on time. By doing this, you will avoid or minimize major repairs on your vehicle.

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