Other vehicle maintenance and repair

Why Is My Car Engine Light On

Michael Riley
By Michael Riley. Updated: September 5, 2017
Why Is My Car Engine Light On

When there is a problem with your car, we normally notice this due to obvious symptoms of a mechanical problem, such as loss of power, jerking or strange noises. Sometimes however, the only sign that anything is wrong is a warning light on our dashboard. If your car engine light has come on, it is very difficult to know what the problem might be without more information.

However there are a few common reasons why your car engine light is on, and with the right diagnostic equipment, a modern vehicle will tell you exactly what has gone wrong. So if you want to know how to diagnose why your car engine light is on, and solve the problem, keep reading and let oneHOWTO explain exactly what to do when your engine warning light comes on.

You may also be interested in: Why Does My Car Lose Power?

So, why is my car engine light on? The Engine Warning Light in you car is an indicator for a system that functions in a similar way to an emissions testing kit. Therefore, if the engine light comes on in your car you can be fairly certain that the problem relates to fuel consumption and/or exhaust emissions.

A steady light generally indicates a less severe issue while a blinking light can indicate a severe problem, but check your owner manual to be sure. Even less serious issues can seriously reduce fuel economy and often lead to bigger issues over time. If the light indicates it is serious, take your car to a mechanic right away and help them diagnose the problem.

Possible causes of engine light on

Although we have stated two of the most common reasons why your car engine light comes on, there are other reasons that may also trigger this light to flicker:

  • Faulty gas cap: When a gas cap turns faulty or goes missing, there could be a leakage in the emission system, which will turn the engine light on. If this is the case, you may also smell fuel around the vehicle, and you'll notice the gas cap does not close properly.
  • Spark plug misfire: If this is the problem, you may also notice your car jerking. Moreover, you will also notice a higher fuel consumption and loss of acceleration power too.
  • Faulty MAF: If this is the reason why your car's engine warning light turns on, you will also find it hard to start the engine, it will stall shortly after being able to start it and you will also notice lean idling.
  • Problems with the catalytic converter: If your catalytic converter is faulty, your gas mileage will go up, thus triggering the engine light to turn on. If you haven't cleaned the catalytic converter for some time,
  • Oxygen sensor malfunction: Another possibility is that there is oxygen sensor problems. In this case you will also have a hard time starting the engine, your car will jerk erratically and you may need to clean the bad oxygen sensor in order for it to work properly again.
Why Is My Car Engine Light On -

Diagnosing the underlying problem

Diagnosing the problem is dead easy if you have the right kit (or know somebody who has). The device you need is called a Car Diagnostic Tool or Code Reader. Most good auto-shops should have one to test your vehicle, or you can buy one yourself fairly cheaply if you would prefer. Just make sure the model you get is compatible with the make, model and year of your vehicle.

To diagnose the problem, all you need to do is connect the diagnostic tool up to the cars engine (the location of the connection should be in the vehicle's owner manual). Once you hook it up, the car's computer will tell the diagnostic tool exactly what the problem is using a code. Whilst it is irritating to have your car engine light come on, taking the right action at an early stage can save you serious cash by preventing damage to your catalytic converter.

Now you know how to diagnose the problem - below we go into more detail about the most common problems and how to fix them.

Why Is My Car Engine Light On - Diagnosing the underlying problem

What to do

The first action you should take when your car engine light comes on is also the easiest. Check your fuel cap is securely attached and that there are no cracks or damage to the seal. It sounds like a simple thing but a faulty fuel cap helps to maintain pressure in the fuel supply system. try tightening the cap and wait 2-3 journeys to see if the light goes off.

Why Is My Car Engine Light On - What to do

If that didn't solve the problem, or if you notice any significant performance issues, try to reduce the workload of the engine by driving gently and avoiding carrying heavy loads or straining the motor, and get the car checked as soon as possible.

Why Is My Car Engine Light On -

If you have taken the steps above and your engine light is still on, there several common components that could need replacing: Oxygen sensors, Mass Air Flow Sensors, Spark Plugs and Connectors or even your catalytic converter. Get the problem diagnosed using a diagnostic tool and get the necessary parts replaced right away.

If you want to read similar articles to Why Is My Car Engine Light On, we recommend you visit our Car Maintenance and Repair category.

Write a comment
What did you think of this article?
Leonard damong
I got p2070 error code IMT control valve stuck open. replaced said parts but still engine light on.
JULEY Wynter-Robertson
I have a 2001 Mitsubishi space wagon, whenever i drive fast up a hill the power cuts, it sounds like an aeroplane, vibrate and the engine check light comes on. i have to stop switch it off for a few minutes and it will go again.
i need your advise its frustrating me
Eloy chavez
I'm having trouble with my truck I don't have power up hills
Tumi Tlhabanelo
My car is got an engine signal on the dashboard and is shaking when it is on,now I took it to different machanices who gave me different diagnosis reports and that shows contradiction and now I am confused as who to trust and where to go? please help
OneHowTo Editor
If this is the case we'd recommend step 2 and diagnosing the problem yourself by purchasing a car diagnosis tool.
This is correct, if you don't own a kit like this and your car engine light is still on, take it to a professional.
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Why Is My Car Engine Light On