Anyone who's ever had a check engine light (also known as a malfunction indicator lamp) appear in their car has probably wondered what to do about it. More often than not, these sensors are related to the vehicle's emissions system. To understand why these errors are so commonly related to emissions, it's important to learn a bit about the systems behind that little yellow light.
It's Not Just an Idiot Light
Check engine lights (CEL) have been around for a while now, but they aren't related to the simple "idiot lights" that inform you of major issues such as low coolant or oil pressure. While even these lights may now be tied to computer systems in modern cars, the original distinction was that the CEL was reporting trouble detected by the car's computer rather than simply illuminating as the direct result of a serious issue.
Since sensors are what allow your car's computer to make engine management decisions, it's easy to see why bad sensor data is the most common cause of computer trouble codes. The actual system behind the trouble codes reported by the computer is known as on-board diagnostics, or OBD. Since all modern cars use the second iteration of this system, it is commonly referred to as OBD2.
What's This Have to Do with Emissions?
The original OBD standard was designed specifically to track vehicle emissions. OBD2 outputs drastically more data and is useful as a general purpose diagnostics system, but that doesn't mean that it isn't true to its roots. Many of the systems and sensors tracked by OBD2, as well as many of its possible trouble codes, relate back to components that are part of your vehicle's emissions control.
On the other hand, it's more difficult for the computer to monitor the state of internal mechanical components. Often, problems with these components only show up as incidental codes. For example, any problem that causes your engine to misfire will trigger a code, but additional clues are usually required to find the true source of the problem. In some cases, serious mechanical issues may not trigger any codes at all.
Meanwhile, a faulty sensor will usually report clearly erroneous data (or simply fail to report any data at all), allowing the computer to immediately pinpoint the source of the trouble. This allows the computer to throw a code that can immediately tell you the source of the problem.
Don't Ignore Emissions Problems
So, can you ignore a problem if it's just a sensor? Unfortunately, the answer is usually no. Not only does your car's emissions system help to minimize air pollution, but it also plays a key role in allowing your engine to run efficiently. Emissions-related problems may not initially cause any obvious symptoms, but over time they will reduce your fuel economy and sap power from your engine. Depending on the specific part that is failing, serious problems will eventually lead to major drivability issues. Even something as simple as a failed O2 sensor will eventually cause serious and expensive damage to your catalytic converters.
If you see that little light come on, remember not to panic. Unlike the other lights on your dash, it likely doesn't spell serious trouble for your engine. It does, however, indicate a problem that will need to be addressed to keep your car running cleanly and efficiently. Reach out to a check engine light service for more information.