Illustrated check engine light

Don’t Fear The Check Engine Light

We made it through the holidays. You’ve taken down all the lights and decorations, or you’ve switched over to calling them Mardi Gras decorations. But another light sits there lurking, ready to strike and ruin all your gluttonous plans—the dreaded check engine light. Well, dread no more! Knowledge is power! Let’s diagnose the problem before it’s too late to get your king cake delivered.

Vehicles Older than 1996 Need Not Apply
If your vehicle is newer than 1996, you’ve likely seen the ominous orange glow coming from your dash. The check engine light always seems to pop up when it is least convenient. Unlike your ex, your car isn’t doing this on purpose. It’s more like a baby crying out for help with the very limited vocabulary given to it by its computer-programmer parents. We all know how limited 1990s parents were with their vocabulary.

If your car is on the newer end of the time spectrum, it may have a slightly upgraded vocabulary and a plethora of other dashboard lights. You’ll want to dive into your owner’s manual to determine subtle differences between these lights to see if they really mean “check engine,” “check powertrain”—any part of your vehicle that makes it go forward—or just “service required,” which likely means you’re due for an oil change.

If the light is blinking at you angrily, this is usually a sign of a big problem that needs to be taken care of ASAP. Remember, the engine is crying out for help. If you can’t address the issue right away, reduce any load you may be putting on it. Ideally don’t drive your vehicle, but if that’s not an option, reduce your speed and don’t tow anything. It is also a good idea to take note of any changes in your car’s performance, like a loss of power or any unexpected sounds or erratic vibrations.

Communicating with a Computer
Once you’ve determined what a check engine light looks like for your vehicle, the next step is to decipher what that even means. It’s not like car manufacturers are expecting you to check the entire engine (although I wouldn’t put that past them). For this you’ll need to obtain an OBD-II (On-Board Diagnostic, version two) code reader, which is just a computer that can talk to the computer in your car and translate it to a language humans can understand. Think of it as a very early model C-3PO that you can plug in somewhere in the driver’s side footwell, under the dashboard.

You can purchase code readers far and wide on the internet, or you can go to your local parts store and they will gladly help you read any codes for free in hopes of selling you more and more parts you may or may not need. If you’re not really a DIY person, you should have a beautiful, blossoming friendship with your neighborhood mechanic. They will gladly diagnose the problem for you in exchange for an hour’s charge of their labor.

Now you have taken the problem into your own hands. Once you have a diagnostic code from your code reader, or your code reader’s code reader (your mechanic), write it down or take a picture. You may find that there are multiple codes plaguing your vehicle and their descriptions may sound scarier than they actually are. Don’t get spooked just yet.

It’s Time for Research
Go forth into the World Wide Web, for therein lies your answer. You will want to search for the code(s) along with the make, model, and year of your vehicle as sometimes there are issues that commonly affect a certain version of a generally reliable vehicle. I recommend doing this first to get any obvious issues that many people have dealt with before you out of the way, particularly if this car is new to you.

Next, consider what these codes mean and how they make sense in light of the sounds, vibrations, or changes to the power of your vehicle when driving. If you are getting a code having to do with the steering system, you will likely also experience some trouble when steering, be it a performance issue or strange noises. This will help you determine whether the problem is mechanical or electrical at its root.

The majority of issues that cause the check engine light (or any dashboard light) to turn on are problems with some kind of sensor. Sensors are electronic components that are typically binary, meaning they are either sensing an issue or not. They can only turn the check engine light on or off in order to communicate with the driver about potential issues. Take this into consideration when you are trying to solve the problem at hand.

Do you really need to replace expensive parts or is there a damaged wire causing the sensor to malfunction? Sometimes the check engine light will turn on or off by itself, either from a loose connection or a sudden change in temperature, humidity, or atmospheric pressure. While you might be able to find and fix a loose electrical connection, changes in the weather are not something anyone can control.

OBD-II systems have made a lot of people purchase parts and pay for work that they didn’t need, all because they trusted a computer to do the diagnostic work for them. These systems can be incredibly helpful, but they are not a replacement for a human brain and some basic car knowledge. Sometimes all you will need to do is tighten your gas cap and the “check engine” light will turn off all on its own.

Common Error Codes
P1028 – Coolant Thermostat: This means the temperature of your engine has not warmed up or not warmed up enough to the level that is normally expected. This could be a problem with the sensor taking the temperature reading, the thermostat which lets coolant flow in and out of the engine, a leak or clog in your coolant system (like your radiator), or an engine cooling fan which is stuck on. Start by eliminating the easiest and cheapest repair first: Check your coolant level and see if there are any puddles of coolant under your vehicle. Double-check for coolant leaks with your car running, as this will put the coolant system under pressure. Sometimes just adding a bit of coolant if you’re low will clear this code on its own. If it doesn’t, further research will be necessary.

P0171/P0174 – System Too Lean: This means the fuel to air mixture, which is being constantly adjusted, has more air than fuel. If you are seeing this code, your vehicle probably has trouble idling, especially when it is at running temperature, and can even die when you’re sitting at a stoplight or in traffic. This means not enough fuel is getting into the engine cylinders which could mean a clogged fuel filter, a weak or dying fuel pump, clogged fuel injectors, or you have a vacuum leak which means extra air is being sucked into the engine.

P0300 – Cylinder Misfire Detected: This means there is some sort of problem preventing at least one of your engine’s cylinders from firing correctly, or maybe keeping it from firing at all. In other words, your vehicle isn’t running on all cylinders. In most cases, you may not be able to notice a misfire unless you are extremely attuned to your car’s regular sounds and vibrations. In other cases, you might feel loss of power particularly in higher gears or a rough idle. This can be caused by a large variety of issues. It could be due to spark plugs or spark plug wires being old, corroded, or worn out, which means there is no spark to light the fuel for combustion. Maybe your fuel injectors are clogged or your fuel pump is pumping an incorrect fuel amount, be it too little or too much, into the cylinder. It can also be caused by a vacuum leak adding too much oxygen to the mix. In the worst case scenario, it may indicate that there are some major issues with the internal parts of your engine which might end up requiring a full engine rebuild.

Don’t Let it Linger
This is not to discourage you from diving deep into exactly what your vehicle is trying to communicate with you. If the check engine light remains on without being addressed, it can mean much bigger issues down the road. Continuing to ignore the warning—even if you have determined the warning to be benign—without addressing the underlying issue may hide other more dangerous diagnostic codes that pop up, which can lead to more expensive solutions. It’s a lot easier to fix one issue at a time than to try and solve a web of interconnected issues while trying to find the one at the root of the whole mess. Even if you are not planning on doing any mechanical work yourself, being able to reason through why a particular code is popping up can help you communicate important information to your mechanic, making their job easier and saving you a few hours of their labor cost.

Owning a car may feel like playing whack-a-mole with repairs at times, but keeping a vehicle running in good condition can benefit you and your community in countless ways. Not only can you access more opportunities with increased mobility, you can help lift up others around you. It takes a village to keep any of us going, so why wouldn’t it take a village to take care of a vehicle? I hope your New Year’s resolution is to practice the opposite of rugged individualism. Let’s choose compassionate collectivism every chance we get.

Got questions about your car, truck, SUV, or other engine-powered vehicle? Email

illustrations by Deanna Larmeu


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