Why is the Check Engine Light On?

Why is the Check Engine Light On?Few things related to your automobile can be as disheartening as the check engine light coming on. While many people fear the worst as soon as this light comes on it may actually be only a small problem. However, that little issue will grow worse if it is not addressed so be sure to get to the repair shop right away. In this list of common check engine problems we start with a worst case scenario.

Catalytic Converter

The catalytic converter is designed to convert hazardous exhaust fumes into less harmful emissions. It will almost never become damaged unless some other part or sensor fails first, which would cause excessive amounts of unburned fuel to travel through it. If the check engine light diagnostics reveal a faulty converter it is likely the light has been on for some time and now you're in for one of the most expensive types of auto repair.

Oxygen Sensor

The oxygen sensor is one of the things that can cause a catalytic converter to go bad. This sensor is located in the exhaust system and monitors how much O2 is in the exhaust in order to help dictate how much fuel is sent to the combustion chamber. If it fails or if there is an exhaust leak it will read excessive oxygen, thus sending more and more gas to the engine.

MAF Sensor

On the other end of the car is the mass airflow sensor, which measure the amounts of incoming air and calculates how much should be mixed with the gasoline. A failed MAF sensor can also cause the car to run rich, thus lowering your MPGs and damaging other parts.


Misfiring, which results in lowered fuel efficiency and a rough running engine, is usually caused by dirty or corroded spark plugs or spark plug wires, or possibly because of failing ignition coils, as well as other minor issues. Most misfiring problems can be repaired quickly and inexpensively.

Broken or Loose Gas Cap

Your best case scenario is if you simply forgot to tighten the gas cap after filling up. A loose, ill-fitting or broken gas cap can result in fuel evaporating out of the filler hose, which will be detected by vehicle sensors, thus triggering the check engine light.

When the check engine light comes on don't hesitate to get to the shop for service. For accurate check engine light diagnostics in Newberg visit Doran Automotive. We excel at providing fast and proper auto repair services for all makes and models. To learn more or to request an appointment for professional auto repair in Newberg give us a call at (503) 476-3892 today.

Doran Automotive Blog

Published By MORBiZ