Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. The Check Engine Light Demystified

The Check Engine Light Demystified

check engine light demystified

There’s one little yellow light that strikes fear in the heart of every driver. It casts a shadow of doubt over your whole vehicle. Will this be something straightforward or will the repair bill put you in debt?

The Check Engine Light has long puzzled drivers with its vague warning. When it illuminates, it's unclear if you should continue driving or get your car towed. Here’s everything you’ve wanted to know about the Check Engine Light:

What the Check Engine Light Does

The Check Engine Light has one purpose: to tell you when you have a problem. That’s all. It doesn’t tell you what the problem is; a technician will have to perform a diagnostic scan to check the affected system. It only indicates that something isn’t working properly.

The Check Engine Light is also known as a malfunction indicator light. It’s shaped like a motor and is yellow in color. Most vehicle systems run self tests under certain operating conditions, and the results are reported to their respective control modules. If a self test fails under certain parameters, your car’s Check Engine Light will come on. It could be an engine, transmission, or emissions system that didn’t pass the test.

What Does the Check Engine Light Mean?

There are two different ways the Check Engine Light can come on: solid or flashing. They mean two different things.

If the engine light comes on and flashes, that indicates an immediate concern. You need to find a safe place to pull over and turn your vehicle off. You may want to consider getting it towed to the shop. A technician needs to diagnose the concern at the absolute earliest convenience to prevent damage to your car. A flashing Check Engine Light is serious business.

If the engine light comes on solid, it may still be a reason for concern, however it doesn’t immediately need to strike fear in your heart. A solid Check Engine Light can mean something like a loose gas cap, or it can indicate a more in-depth problem like a fuel, timing, or transmission issue. Get your car diagnosed, although the urgency isn’t the same as if the light was flashing at you.

Common Reasons the Check Engine Light Comes On

The reason for an engine light can be a risk of catastrophic failure or something requiring immediate attention, or it could be nothing at all. As the car’s systems run self-tests, it is possible that a test fails and the engine light comes on, and the next test passes. The Check Engine Light may not turn off as soon as it passes, and it may not even turn off until a technician clears the code even though there is no repair required at all. Common reasons for the Check Engine Light are:

  • The gas cap was left loose when refuelling
  • Emissions-related sensors, such as oxygen sensors, have failed
  • Engine timing problems, most commonly with variable valve timing
  • Transmission failure codes
  • Engine misfire codes
  • Catalytic converter problems

There are literally dozens, if not hundreds, of other reasons for the Check Engine Light to come on. If it illuminates, have it checked out expediently. Don’t take unnecessary chances if it feels like the vehicle is not operating in a safe manner. Have your vehicle towed to the shop if you don’t feel safe driving it. If the Check Engine Light is flashing, it is in your best interest to cease driving until the light has been diagnosed and repaired.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P0291OBD-II Trouble Code: Cylinder 11 Injector Circuit Low
P0291 code definition When your vehicle’s PCM registers the P0291 code, it means that a voltage reading came from the fuel injector circuit – for cylinder number 11’s fuel injector –...
P0477 OBD-II Trouble Code: Exhaust Pressure Control Valve Low
P0477 code means that the PCM has detected an abnormally low voltage reading often due to the exhaust back pressure control valve circuit.

Related questions

Q: engine misfire. 1995 Toyota Corolla

Hello. These types of issues can be hard to diagnose. Most of the time they are caused by a failure within the distributor itself. Also common is the shaft being slightly worn, which will cause the RPM reading to be...

Q: RPM/engine issue.

The engine's computer should be scanned first to see if there are codes pointing to the cause of the RPM problems and the no start. If the codes are tested and no problems are found then try and disconnect the...

Q: I have gray smoke coming out of my tailpipe but it's not heavy smoke and my car check engine light is orange​ my car shut off

You did not mention why the radiator was replaced but I think your engine was overheated causing the head gasket to go bad. This would cause the white smoke out of the tail pipe and an engine misfire and overheating...