Marple's Hometown Monthly Magazine
Mailed to homes and also read online!

Why Your Check Engine Light Comes On

Marple Friends & Neighbors, July 2022

The check engine light is a signal from your car’s engine computer that something is wrong with the engine emissions system. Generally, when it’s on, your fuel economy and engine performance may be at risk. Unfortunately, the light is not specifically helpful because a typical internal combustion engine has around 200 parts! 

To diagnose exactly what may be wrong, you would need to use an Onboard Diagnostics-II (OBD) reader (aka scanner) to get the specific diagnostic code, and then research the code’s meaning. However, you should think of a diagnostic code like a ZIP code and the issue like a specific house in that ZIP code. Your mechanic will be able to pinpoint the exact issue (house) and complete the necessary repair(s). 

When the check engine light comes on, you don’t need to freak out, but it is important to promptly address it. Ignoring it could lead to larger, costlier problems later. However, if it’s flashing instead of being on steadily or continuously, your issue is a bit more urgent! 

While your check engine light may come on for various reasons, here are the five most common reasons why that light comes on in our area of the country. 

  1. Oxygen Sensors (O2S)

When your O2S needs to be replaced, your car will either run rich (less oxygen, more fuel) or lean (more oxygen, less fuel), both of which are bad for your car and the environment. If this oxygen/fuel mix is faulty during an emissions inspection, you’ll more than likely not pass.

  1. Catalytic Converters

Over time, a vehicle’s catalytic converter can become clogged, which restricts exhaust gasses from passing through properly. Some symptoms include reduced acceleration, dark exhaust smoke and the smell of rotten eggs coming from the exhaust. 

  1. Loose Fuel Cap

If your check engine light turns on immediately after a fill-up, pull over and make sure the fuel cap isn’t loose. Yes, it can be that simple! Over time, the cap will wear down and may need replacement.

  1. Ignition Coils and Spark Plugs 

As your vehicle ages, these parts may corrode or simply wear down and not perform their best. Worn or faulty ignition coils and spark plugs can cause issues like engine misfire, hesitation under heavy acceleration or even making the engine shut off unexpectedly. 

  1. Mass Air Flow (MAF) Sensor 

Your check engine light may be on because no accurate signal is coming from the MAF sensor. Without it, your car won’t know how much fuel to give the engine. This could cause the engine to run rich or lean and ultimately cause the engine to run rough and misfire. A bad MAF may also reduce your vehicle’s acceleration and lead to an increase in fuel consumption.