Why is the Check Engine Light On in Your Subaru?

The best way to tell what caused a check engine light to come on is to hook up an On-Board Diagnostic (OBD) code reader. Since 1996, every vehicle has been equipped with an OBDII port where a code reader can be hooked up to read any codes the vehicle's computer has encountered. These codes will tell a technician what is wrong, or at least what caused the check engine light to come on.

While these code readers are available for sale, they are expensive. What's more, they won't go far in actually fixing any real problems, and you may still need to translate the code into something that's understandable. These are among the reasons that it's typically better to take your vehicle to an authorized dealer when a check engine light comes on. There, you'll find OBDII readers specific to the brand of vehicle and the technicians who know what they're doing.

What are Some Common Reasons for a Check Engine Light to Come on?

The check engine light comes on when the vehicle's computer detects a problem. This is generally determined by information it gets from a variety of sensors. Often, replacing the sensor is all that's necessary for the problem to be resolved. The check engine light will then be reset and not come back on so long as the problem was sufficiently addressed

O2 Sensor

One of the most common sensors to cause a check engine light to come on are the O2 sensors in the exhaust system. They endure significant heat and soot from the exhaust system that will eventually require them to be replaced. This sensor provides information the computer needs to determine the precise air and fuel mixture needed in the engine.