What to do when the Check Engine Light is on

No matter if your car is brand new, or has a few hundred kilometres under the hood, sooner or later you'll see the Check Engine light on your dash. Modern cars can self-diagnose the mechanical and electrical issues and warn the driver when there is an issue. You no longer need to rely on smells, rattles, and squeaks to figure out there's an issue. There's no need to fear the warning light though, remember it's there to help.

What does it mean?

When you see that dreaded picture of an engine with “Service Engine Soon” on the dash it's from your car’s computer, called the powertrain control module (PCM). Just because the light is one, doesn't mean your car’s having an emergency though. It’s just a signal to remind you there could be an issue and to get some assistance sooner then later. Depending on the severity of the issue, the light may look a little different. Usually the light will be amber or orange and continuously lit, while a severe problem may result in a red or flashing light.

When the light goes on, first check other instruments in your car to see if there is a more serious problem. Start with the oil light and coolant temperature gauge. There are likely other lights that indicate issues with other systems, like the antilock brakes light. If you’re not sure what a particular light means, check your owner’s manual.

If the problem is severe, the Check Engine light will likely flash. If this happens you should pull over as soon as it's safe to do so. Your car might also enter “limp home mode.” which means your car typically won’t shift gears and your speed will be drastically limited, just giving you enough to get home. Although you should stop driving, this is your actually car’s way of limiting damage if it has a serious fault, so no need to fret quite yet.

Common Causes

There are tons of possible problems that can cause a Check Engine light. Often it's related to the car’s emissions-control equipment. Keeping cars from over-polluting requires a complex system, and this is constantly monitored by the car’s computer. How sever the emission faults are can vary, but do not necessarily mean you should stop driving your car.

If your Check Engine light comes on, the first thing you should check are any areas of the car that you or someone else recently interacted with. Things like the gas cap, oil-fill cap, battery, and air-filter to look for obviously disconnected wires. If anything is loose, improperly attached, or disconnected, the computer will detect this as a system fault and warn you through the light.

What do you do?

Resist the temptation to reset your Check Engine light by disconnecting the battery. Even if you manage to turn off the light, that doesn't mean you've solved anything and may only mask the issue. Your car’s computer will have diagnostic information available as 5-character codes, starting with the letter “P,” but those could be lost if you reset the light prematurely. For intermittent problems, reading the codes saved in the car’s computer may be the key to the ultimate fix.

To read your car’s stored codes, you or a mechanic will need a code reader to plug into the computer, located low on the dashboard, below the steering wheel on the driver’s side of the car. It's known as an OBD-II (on-board diagnostics) port. Finch Used Cars always used professional-grade scanning tools, but many simple code readers can be found for less than $25, and one should be in every DIY mechanic’s toolbox. The hard part is understanding the code and finding out the severity of the issue and what to do next. Luckily, the skilled mechanics at Finch Used Cars can read your code(s) and give solid advice on how to proceed.

If you want to gather information on your own, a web search using your car's specific code(s), year, and model can also give you a base idea. But if you’re unsure, it's best to come in and see one of our experienced mechanics for a full diagnosis.

The Bottom Line

Don’t fear the Check Engine light! It’s an indicator that makes repairing your vehicle easier and helps it run longer. It's good to also pay attention to other signs and symptoms that come along with the light, as these may be a better measure of the severity of you vehicles issue. Use an OBD-II code reader to extract the codes from your car’s computer, and let them lead you to the ultimate repair.