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What Does a Check Engine Light Flashing Mean?

A check engine light illuminates on a vehicle dashboard.

Modern vehicles are amazingly adaptive to situations that would have caused havoc in older cars. A network of sensors constantly monitor systems across the vehicle and make minute adjustments to keep things running at peak efficiency. Those same systems can also sniff out trouble. If something is wrong with your car, you definitely want to know about it. Still, the sudden and unexpected illumination of the check engine light (also called the malfunction indicator lamp or MIL) can create a unique sense of dread. Our fears aside, the car is trying to tell us that something isn’t right, and we’d do well to pay attention when the light comes on. But what if you find your check engine light flashing? Is that any better, or is it worse?

Purpose of the Check Engine Lightcheck_engine_MIL_warning_light

Your car has a system of sensors monitoring different components and activities that’s in constant contact with the vehicle’s onboard computer. The computer analyzes signals from the sensors to make any necessary changes via actuators in the system. When something is wrong with the vehicle that it cannot correct, it will let you know by a flashing engine light on the dash.

The blinking check engine light could be due to something specific, like a flat tire or low coolant, but there are a number of engine problems that will show up under the catch-all “check engine” light. When this happens, the computer logs a fault code in its memory, which can be accessed using an OBD II scanner. Many shops will run this scan for you, but it’s also pretty straightforward to purchase a diagnostic scanner and pull the codes on your own. Note that just having a code in hand doesn’t mean you’ve identified the underlying issue. A code can help point you in the right direction, but more diagnostic and repair legwork will likely be needed. Sometimes multiple codes may be found which calls for careful deductive reasoning as to whether the issues are related to each other, or just happen to be a coincidence.

Solid Light vs. Flashing Light

Sometimes a solid check engine light will turn on for something of less consequence, like a loose gas cap, but more often it’s due to something more serious than that, and you simply won’t know what the cause is unless you get a scan. Be sure to get a scan as soon as possible so you can start figuring out whether you have a serious problem or not.

A flashing check engine light is especially meant to get your attention and likely points to something that cannot wait. In fact, if your check engine light is flashing, you may want to consider changing your plans and driving to a mechanic immediately. Your vehicle is making no promises of getting you to your destination with that blinking engine light, so you may even need a tow.

Check, Check

A flashing check engine light often indicates a misfire, or that at least one of your cylinders isn’t going through the combustion cycle properly. This could mean that you’re building up a lot of unburned fuel and excess heat. Aside from being a firestarter recipe, this can also cause serious damage to costly components, such as the catalytic converter, if it continues. While a flashing check engine light might seem like a small problem, it can quickly turn into a larger one if it goes ignored. Just because the vehicle is still running does not mean everything is okay. As previously mentioned a modern vehicle can adapt to keep running even if doing so may cause further damage. Typically the vehicle will default into “limp home” mode which reduces power to help protect the drivetrain. The function of “limp home” is just as it sounds, just enough operation to get you home or somewhere safe to park and arrange repair service.

Just like service lights and solid engine lights, a flashing check engine light has codes associated with it that can be accessed with a scanner. In the past a You can use  a scanner to get the codes for diagnostic purposes, but don’t run the vehicle any longer than you have to, or you might risk more serious damage. The safest option is to see a mechanic as soon as you see your check engine light blinking. They should be able to diagnose and repair the issue so you can get your car back on the road. If your check engine light went off by itself it is still a smart idea to get things checked out. The self-diagnosis systems in most vehicles will store a potential error code in memory and wait to see if the problem happens again. If it does then it will activate the check engine light. Investigating stored error codes can help head off potential future problems.

Lastly it may be tempting to turn off the check engine light via a diagnostic scanner but that does not fix the underlying problem. Resetting a check engine light will force other systems back to a basic status and require a few driving cycles to get back to normal. This could be a problem if the vehicle is in an area that requires emissions testing as these systems will be set as “not ready” and cause the the vehicle to fail the emissions test.

An Ounce Of Prevention

One of the best ways to avoid getting to the point of a blinking engine light is to commit to regular maintenance checkups. Making sure spark plugs and wires are good, changing fuel filters, and checking that injectors aren’t clogged can all help to prevent misfires. Sometimes something as simple as a loose gas cap can trigger an engine light so make sure it is tightened with every fill-up.

Check out all the diagnostic tools and equipment available on NAPAonline, or trust one of our 17,000 NAPA Auto Care locations for routine maintenance and repairs. For more information on a check engine light flashing (or engine light blinking), chat with a knowledgeable expert at your local NAPA Auto Parts store.

Photos courtesy of Flickr.

Blair Lampe View All

Blair Lampe is a New York-based professional mechanic, blogger, theater technician, and speechwriter.  In her downtime she enjoys backpacking wherever her boots will carry her, rock climbing, experimental theatre, a crisp rosé , and showering love on her 2001 Sierra truck.

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