Why is the Check Engine Light On?


Your car is quite a feat of engineering. Not only can it take you from home to work or across the country with relative ease, it can also detect many of its own faults. Numerous sensors around the vehicle are constantly on the lookout for possible failures that could decrease efficiency, reliability or safety. Many of those sensors, should they sniff out a possible problem, will trigger the check engine light. Let's look at a few of the most common causes of check engine light illumination. Remember though, get to the auto shop for diagnostics as soon as the light comes on, as putting off services can cause the problem to get worse, as represented by this first issue.

Failed Catalytic Converter

The catalytic converter has a tough job; it turns hazardous exhaust fumes into less harmful emissions. Should this part fail, replacing it can be very expensive. One of the most common causes of catalytic converter damage is excessive exhaust fumes passing through the exhaust system due to the burning of excess fuel. This is an issue that could develop if one of the following two problems took place first, both of which would have triggered the light long before the catalytic converter was damaged. Fixing either issue is much more affordable than replacing a catalytic converter, which is why you should always visit the shop for diagnostics as soon as the check engine light turns on.

Malfunctioning O2 Sensor

The oxygen sensor is a part of the exhaust system that is constantly monitoring the amount of oxygen within the exhaust fumes. This analysis is then used to calculate the proper air and fuel mix for the engine. A malfunctioning o2 sensor can result in more gasoline being burnt than necessary, which, as mentioned, damages the catalytic converter.

Failed MAF Sensor

The mass air flow sensor is similar to the oxygen sensor except it is placed at the front of the vehicle and monitors incoming air opposed to outgoing. It's job is to measure the volume of air coming into the car to determine how much needs to be mixed with the gas inside the combustion chamber. If the MAF sensor malfunctions it too could cause extra burning of gasoline, resulting in a loss of fuel efficiency, poor engine performance and possible damage to the catalytic converter.

Cylinder Misfire

Misfiring is what occurs when the spark plugs are not firing at the precise moment they need to for maximum efficiency and power. This can be a result of spark plug corrosion, worn ignition coils, bad spark plug wires and other various issues. This will be a noticeable problem as it will cause your engine to run rough and may cause your engine light to flash.

Loose or Cracked Gas Cap

The best thing you can hope for when the check engine light comes on is that you forgot to tighten the gas cap the last time you filled up. A loose or broken gas cap may allow for fuel vapors to evaporate out of the filler hose, causing the light to come due to the EVAP system sensing the leak.

It is important to have check engine light diagnostics conducted by a professional auto repair shop as soon as it comes on to prevent issues from growing worse. If you need check engine light diagnostics in Cumming, GA, for your BMW, Mercedes or other European car, head to G2 Automotive. Our European auto repair exerts use the latest auto diagnostic and repair technology to ensure fast and accurate fixes. Give us a call at (678) 771-6434 to schedule an appointment or to request an estimate for the cost of European auto repair in Cumming or the surrounding area.


G2 Automotive Blog
Posted: November 26, 2020

Written and Published By MORBiZ


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