The Check Engine Light: A Misunderstood "Good Guy"

Check engine lights….we’ve all had them....we’ve all had anxieties because of them. But “check engine” is vague….what could be wrong? Should I be worried? Do I need to do this NOW, or can it wait until I can get it looked at?



The check engine light is also called the “Malfunction Indicator Lamp” (MIL)….which, again, sounds serious but is also pretty vague. WHAT is malfunctioning? Is my trusted vehicle breaking down? It’s important to remain calm and look for anything else which might be noticeable concurrent with the warning light. Ask yourself the following:

Are there other issues which became immediately apparent when the check engine light came on? Any change in performance or handling? What was going on when the light came on: Was I starting up? Did I just get fuel? Was I just rolling along normally when it came on? TAKE NOTE OF ALL THE DETAILS! Are any other lights coming on? Do I notice ANYTHING out of the ordinary after it came on?

We advise you to think about these things and make a mental or written list as you head in to have the problem diagnosed by a professional. The more you can tell your service advisor, the more data they can pass along to the technician, and that can assist with proper diagnosis. If you’re close, we recommend you stop by to see us, but, if you’re not close, find someone else close by. WE CARE ABOUT YOUR SAFETY!

So, how long can I (or YOU) drive without getting the car checked? If the check engine light is blinking, the answer is: get into a shop ASAP! But, even if the check engine light isn’t blinking or goes off again, we still recommend putting safety first and getting a qualified technician to have a look at it. If the check engine light is on, it’s likely that you’re releasing excess pollutants, which, at the very least, can impact gas mileage.

So, let’s look into some common causes and look at how serious they might be! First of all, it’s important to realize that check engine lights can indicate a wide range of potential problems, going from fairly minor, easy fixes to more serious issues that could necessitate repairs. It’s important not to simply ignore them, even if the causes ARE minor issues. Minor issues, depending on the specifics, can become major ones if left unattended.  

1. Loose or missing gas cap: you might not have thought about it, but your gas cap prevents excess fuel vapors from being released into the air. This also maintains a pressurization of your engine, and the check engine light will let you know if this pressure is compromised. Before taking your car into the shop, you may want to first try removing the gas cap and then re-tightening it to see if that solves the problem.
2. Issues with the oxygen sensor: your engine works around the principles of internal combustion, the ignition of a fuel/air mixture to create controlled bursts which move your pistons. The oxygen sensor monitors how much unburned oxygen is being put out in your exhaust. If the oxygen in the exhaust drops below normal levels, the check engine light will let you know.
3. Issues with the mass airflow sensor: To function normally, air needs to be taken in, combined with fuel, and ignited by the electrical sparks of the spark plugs. The mass airflow sensor determines how much fuel is needed for the amount of air entering the engine. Malfunctioning of this sensor will trigger the check engine light.
4. Issues with the spark plugs or plug wires: If a spark plug or multiple plugs or their plug wires become defective, the check engine light will let you know.  
5. Issues with the catalytic converter: the catalytic converter is responsible for converting toxic carbon monoxide, various nitrogen oxides, and hydrocarbons into less harmful gases such as carbon dioxide, nitrogen, and water vapor. This ensures that the exhaust is “cleaner” and less environmentally harmful. A failing catalytic converter will not only trigger your check engine light, but also lead to reduced engine performance. A rotten egg smell combined with the check engine light can also point directly to a failing catalytic converter.
6. Issues with the vacuum system: a car’s vacuum system uses suction generated by the engine to power various systems. Basically, the pistons pull air into the cylinders during the intake stroke, creating engine vacuum, and, in combination with vacuum pumps and hoses, that vacuum pressure is distributed to power things ranging from power brake boosters and turbocharge wastegate actuators to emissions controls. As this represents a critical engine system, a leak or loss of pressure will trigger a check engine light.
7. Issues with the exhaust gas (ERG) recirculation valve: this system works with the catalytic converter to reduce the amount of nitrogen oxides released in your car’s exhaust. Malfunction of the ERG valve will trigger a check engine light.
8. Issues with the car’s battery: if a battery has gone bad and needs to be replaced, it will trigger a check engine light that is generally accompanied by difficulty in cranking the engine on startup. 

So, a check engine light can mean many things ranging from gas caps being too loose or cracked to problems with vacuum pressure which can impact multiple downstream systems to emissions problems which can make our engines function less optimally while contributing to pollution. It’s truly a “misunderstood good guy” that can let us know there are issues with multiple systems that keep us and those around us safe.