Check Engine Light Meaning


When the check engine light comes on in your car, it can be a scary thing. That little amber light will pop on in our dash to let us know something is wrong, but it will tell us much more than that. In this article, we will explain why the light is so important, what it means and how to diagnose the problem. Also, we will show you how to reset the light once you have corrected the problem.

What could cause the check engine light to come on?

Besides typical warning lamps such as ‘low oil pressure’ or ‘engine temperature’, modern cars have a second set of indicators. These are known as malfunction indicator lights and are usually amber colored. They let us know when there is a problem within one of the systems monitored by the car’s onboard diagnostic computer. The ‘check engine’ light is one of these. It will illuminate automatically whenever a possible trouble with one of the following systems is detected:

  • Emission control system
  • Fuel mixture
  • Engine performance
  • Electrical circuits
  • Drivetrain

Is it safe to drive your car with the check engine light on?

The main problem with a ‘check engine’ light is that it does not tell much on it own. The light coming on does not necessarily mean you have a big and expensive problem. Still, there is no place for panic as you can rely on several simple tricks. Observe how your car behaves and look for symptoms such as:

  • Rough running
  • Engine misfire or juddering
  • Lack of power
  • Poor throttle response
  • Unusual sounds
  • Smoke from the exhaust
  • Overheating

Any of these symptoms indicate that the engine in your car is not working as it should.

Is the check engine light serious?

With the logic behind the ‘check enginelight being seemingly vague, you will probably wander how long can you drive with check engine light on. Should you stop and call in a tow truck, or is it safe to finish your trip? In general, if there are none of the symptoms described above, you should be able to drive your car for next few days. However, have it checked as soon as possible.

Lastly, you should have no doubt if the ‘check engine’ light is flashing, as this indicates a severe engine misfire. This can result in expensive engine repairs if not addressed, so never drive your car if the ‘check engine‘ light is going on and off intermittently.

What are the codes for check engine light?

Every time the ‘check engine’ light comes on, a specific 4-digit code will be stored in the engine computer. This code contains the information that will help you quickly and easily pinpoint what triggered the ‘check engine’ light. So, when the ‘check engine’ light comes on, your first step is to read these codes. One option is to take your car either to a local dealership or an independent workshop for a full diagnosis. However, as most workshops will charge this, you should consider purchasing your own scan tool. You may imagine that this is an expensive and complicated piece of equipment, but you would be wrong. All 1996 or newer cars are OBD-2 models, so any scan tool with OBD-2 capabilities can read and clear stored codes. And these scan tools come in all shapes, sizes and prices to choose from. The choices range from something simple as a Bluetooth OBD adapter that connects to an application on your smartphone, over dedicated hand-held scan tools to powerful diagnostic tools. Additionally, there are various part stores, such as AutoZone, where you can lend the scan tool charge-free.

One thing you should never do is clear fault codes without reading and writing them down. Usually, fault codes will be stored together with various parameters, such as engine temperature, speed and load. This information can be vital for a proper diagnosis. By deleting the fault, you also erase that information. That can make check engine light diagnosis even more difficult than it already is.

How to reset the ‘check engine’ light?

As the ‘check engine’ light is triggered by an engine component that does not work properly, you must deal with the source of the problem before trying to reset the ‘check engine’ light. Otherwise, a ‘check engine’ light will just keep coming back, no matter how many times you reset it. There are several ways to reset the ‘check engine’ light:

  • On older cars, the ‘check engine’ light will reset automatically as soon as the problem has been corrected.
  • On some more complex cars, the onboard computer will recheck the conditions that initially triggered the ‘check engine’ light for a certain amount of time. This means that the car will need to be driven for several miles and turned off and on for several times until the ‘check engine’ light eventually goes off.
  • Disconnecting a car battery for several minutes is an old, but in many cases, well proven method. Disconnect both battery poles and then press the horn for about a minute to drain the remaining electricity.
  • Using an OBD2 scan tool is actually the best and quickest way to reset the ‘check engine’ light. Not only can you delete stored codes, but you can also make sure there are no new codes stored within computer memory.

Additionally, there is a neat little trick if you have a scan tool available. Read and write down the codes and delete them. In some cases, a system glitch or a similar one-off event might trigger the ‘check engine’ light. If the code and ‘check engine’ light do not reappear in the next several days, you can forget about it.

In the end – what does OBD stand for?

You may be wondering why your vehicle needs a computer system and what it does exactly. Beginning in the early 1970s, car manufacturers were required to lower vehicle emissions. In the early 1990s, the EPA mandated that any vehicle so within the United States must comply to a new standard called OBD2. It stands for onboard diagnostic system 2. All vehicles made during or after the model year 1996 have to comply with the OBD2 standards. An engine management system such as OBD2 can be divided into three main parts. The inputs or sensors monitor a wide variety of conditions that could affect engine operation. This information, in terms of voltages and resistances, is fed to the main computer. This processing unit is programmed to analyze all of these inputs simultaneously and make determinations on how to alter the fuel ratio and ignition timing of the engine as well as when to ship the transmission to another gear. The outputs are primarily fuel injectors, ignition coils and transmission shift solenoids. Whenever there is a problem in engine operation, a specific trouble code is stored in computer memory. The OBD2 system uses a standard connector, so the diagnostic information can be obtained from any vehicle using any OBD2 diagnostic tool.

Click here to get an check engine light scanner tool for your vehicle.


About Bojan P

My name is Bojan - I am a car enthusiast, specialised in the vehicle diagnosis, repair and maintenance with 10 years of practical, hands-on experience. In addition, I have a Masters degree in mechanical engineering.

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