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

Veteran and Military Driver Laws and Benefits in Idaho
The state of Idaho offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch in the...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...


Related questions

Q: Multiple cylinder misfire

Engine misfires can be caused by many different problems, but there are a few suspects that occur more than others. Generally, misfires are caused by either a spark or fuel issue or in cases, a combination of both. Spark related...

Q: Engine loses power, shuts off

Hello there, losing power in this manner is not usual for the BMW 535i. The fuel pump warning light on your vehicle comes on when the computer detects lower than normal fuel pressures. Many different faults can cause this low...

Q: The computer (ECM) says it's EGR flow and there is no other symptoms. What you think is the problem?

Either the EGR (Exhaust Gas Recirculation) valve is stuck in the open position or is closed and not opening. First try removing the EGR valve and cleaning it out. Then see if the engine light goes out after cleaning the...