Common Reasons for Your ‘Check Engine’ Light to Go On

You’re driving along on the highway and suddenly the check engine light comes on. If this has never happened before you may begin to panic, thinking that your car will suddenly stop. Relax. Unlike other warning lights on the dashboard, the check engine light typically doesn’t signal an emergency. You’ll be able to drive a few more miles, and even a few more days if you can’t get it into your mechanic right away.

Yet it’s important to have your mechanic check out the reason why the check engine light became illuminated because if it’s let go, costly repairs may ensue. Most cars have an onboard diagnostic system that produces error codes. Your mechanic will plug a small computer underneath your dashboard to determine what is causing the problem. Although there are dozens of reasons why the engine check light may come on, here are some of the more common ones.

Oxygen Sensor

Failure of this part is the most common reason for an illuminated check engine light. This part monitors unburned oxygen from the exhaust and helps determine how much fuel is burned. A faulty sensor doesn’t provide the correct data to the car’s computer, causing a decrease in gas mileage.

Most vehicles have between two and four sensors. Faulty oxygen sensors also cause an increase in emissions. Not replacing a broken sensor can eventually lead to failure of your catalytic converter, which can cost more than $2,000 to replace.

Loose or Faulty Gas Cap

When a gas cap is loose or cracked vapors leak out, affecting the entire fuel system. This problem causes a reduction in gas mileage and increased emissions. If your car isn’t jerking or acting strangely when the engine light comes on, pull over and check to see whether it has any cracks or if it is tight enough. If looseness was the problem, the light should turn off within 10 to 20 miles. If cracked, the cap is easy and inexpensive to replace.

Catalytic Converter

This is the expensive item to replace if it goes faulty. The catalytic converter reduces exhaust gases, converting carbon monoxide and other materials into harmless compounds. If it fails completely, the car won’t be able to run.

Mass Airflow Sensor

This part tells the car’s computer to add fuel to the system based on air coming into the engine. A faulty unit causes increased emissions, can result in stalls and lead to decreased gas mileage.