March 1, 2021
Have you ever had your Check Engine Light come on and wondered whether you should keep driving or not? What could happen if you ignore it? How long before you should get your car looked at?

What does the Check Engine Light mean?

Any time that the Check Engine Light (CEL) is illuminated, it means that your vehicle is potentially creating excessive pollution.  Whether it’s your transmission not shifting right, a loose fuel cap or a bad spark plug, these will all potentially cause excessive fuel consumption or possibly raw gas to be released into the atmosphere.  More importantly, your car may be emitting excessive amounts of pollution that add to the amount of greenhouse gases in the environment, potentially increasing smog.

Certainly there are some situations where the CEL coming on is far more critical than others.  Misfiring cylinders versus a loose gas cap, for example, have completely different outcomes if not repaired immediately.  And, consequently, they could have greatly differing effects on the environment if left as is.  Below we will help you determine how urgent it is to see the “car doctor” when this annoying light appears on your dash.

What is the Purpose of the Check Engine Light?

Since 1996, vehicle manufacturers have had to integrate on-board “self-testing” for any car built for North America.  What this means is that, as you drive or run your engine, your car’s computers are constantly monitoring and testing all of the devices that make the engine run and the car drive, attempting to identify faults that could cause excessive pollution.  For example, every time you drive steadily on the highway, the computer will run a test procedure that verifies the effectiveness of the catalytic converter.  If the test happens to fail for some reason or another, the Check Engine Light will be illuminated, warning you that there is a fault with the vehicle.  This is only one example of over a thousand faults that could occur related to the constant testing that takes place of vehicle systems and components as you drive.

How Urgent Is It, Really?

When the CEL comes on, there are several different courses of action that can be taken depending on the exact symptoms.  Understanding these can help you, as a driver, determine just how urgent it is to get the vehicle into the shop or if you should really be driving it at all.  Let’s discuss each situation and explain how they are different.

CEL Comes On Steady With No Other Symptoms

When the CEL does come on, it’s important to ask yourself, “Is the car driving any differently?”.  Basically, does it start, run, idle, accelerate, etc., just as it always has?  If it’s acting completely normal, there is a good chance that you don’t need to panic or even stop driving the vehicle.  But, until the cause is diagnosed properly, there will be no way of knowing whether or not the issue could progress into something more serious indicating that the car shouldn’t be driven.  The rule of thumb in this case is to make an appointment at your earliest convenience to have it looked at by a professional.

CEL Comes On Steady With Other Symptoms

So, the CEL is on steady (not flashing) and the vehicle just doesn’t seem to be running the same as it normally does.  Perhaps it’s slow to accelerate, runs rough or idles differently?  Something just doesn’t feel right to you.  In this case, you should limit the amount you drive the vehicle until you can get it in for a diagnostic, and the sooner the better.  The fact that it’s not running right could mean that it could let you down, possibly stranding you far away from home.

CEL Comes On and Is FLASHING

A “flashing” Check Engine Light that either flashes from time to time or flashes constantly while you are driving is indicative of  “engine misfire”.  Misfire means that one or more of the engine’s cylinders are not burning the gasoline properly and that, potentially, raw fuel is making it’s way through the engine and into the exhaust system.  Whenever there is misfire occurring, you run the risk of damaging the engine and/or the catalytic converter.  Engine damage can cost you thousands of dollars, and catalytic converters are not much cheaper in some cases.  The average catalytic converter these days can cost $1500 or more plus installation!  Catalytic converters operate at temperatures between 1500 to 2500 degrees Celsius.  At these temperatures, dumping excess gas into the converter is basically like pouring gasoline on a campfire.  This will cause the converter to get much hotter and risk melting the material it’s made of.  If you run into this situation where your CEL is flashing, even just flashing once in a while, the car should NOT BE DRIVEN.  Tow it to your trusted repair centre and have it diagnosed and repaired right away.  Flashing should not be confused with a CEL that comes on one day and goes off the next.  Flashing refers to when the CEL light turns on and off rapidly many times.

My CEL Has Been On For Years, What Should I Do?

It’s important to remember that there is only one Check Engine Light, and there are literally thousands of reasons as to why it could be illuminated.  When the light is already on, you will be unaware if something more critical develops.  Potentially, you may never know when the CEL progresses from something that is not likely to cause trip interruption to something more critical that could lead to an actual breakdown.

If your car is older and you simply don’t want to fix something that is strictly pollution-control-related, have the fault codes checked periodically to ensure that nothing new and/or more critical has become an issue.  As far as which issues should be repaired and which ones can wait, this is something for you to discuss with your repair centre or simply call or email Car Medics for advice.  We’d be glad to help.

Top Check Engine Light Tips

Tip #1 – CEL Is On, NOT Flashing and Has No Other Symptoms

Provided that your vehicle continues to run normally, make an appointment at your earliest convenience to have the issue properly diagnosed. If symptoms develop, get it in sooner.

Tip #2 – CEL Is On With Symptoms

If the light is on steady and the car just isn’t acting or driving like it normally does, drive it as little as possible until you can get it looked at.  It could get worse and let you down.  Provided the light is not flashing, it should be safe to drive it to a local repair shop.

Tip #3 – CEL Is Flashing

This is indicating a misfire condition and the vehicle should NOT be driven.  Pull over and call a tow truck, no matter how inconvenient it is.  Continuing to drive could cost you thousands more in repairs!

Tip #4 – CEL Is Not a Critical Issue 

So, you’ve had the issue diagnosed and it’s been determined that it’s not a critical fault that needs to be fixed in order to keep driving the car.  You’ve decided that either it’s not an expense you can afford, or fixing it is not worth it for the older car involved.  In this case, Car Medics recommends that you get the fault code checked periodically to ensure that something more serious isn’t developing.  Having the codes checked quickly before you head out on a long trip is definitely advised as well.  Keep in mind that when the CEL is not repaired, you’re vehicle is most likely polluting more than it should be.

Tip #5 – Tape Is Not Recommended (LOL)

You could simply apply black electrical tape, or even duct tape, over that part of the dash that is shining the annoying light into your eyes.  Unfortunately, this will most certainly not fix the problem and it may also prevent you from noticing if the light starts to flash.

If you have any questions, need any advice or would like your Check Engine Light or any other warning light diagnosed properly the first time, contact Car Medics.  Give us a call or send us an email and we’ll do our best to help you!

Car Medics has been in business for over 27 years, serving Kingston and surrounding areas. We are experts at all aspects of automobile repair, including diagnostics.

“We Are Always Accepting New Patients”

Two locations to serve you better:

Call 613-547-8473 for Kingston location

Call 613-546-6766 for Glenburnie location

Stay safe and healthy!



Monday-Friday: 8am - 5pm


Need your car serviced?