7+ Main Causes of Check Engine Lights

7+ Main Causes of Check Engine Lights – While it is often assumed that a car’s check engine indicator light (CEL) is an indication of a major mechanical problem, this is not always the case. In fact, according to many professional mechanics, warning lights can be caused by minor electrical disturbances. However, whenever the check engine indicator flashes on your dashboard, it is something to be taken seriously.

Read more: ECM vs PCM vs ECU what are the differences?

7+ Main Causes of Check Engine Lights


The car’s check engine indicator light is triggered when your computer or vehicle’s ECU detects an error originating from one of several sensors in your car, truck or SUV. When this happens, the ECU generates and stores an OBD-II diagnostic trouble code, which then illuminates the CEL. When you take your car to a mechanic, they will download this OBD-II code to give them a starting point for diagnosing the root cause and completing the correct repair. Now that we’ve explained why – let’s dig into the reason a car’s check engine indicator lights up, and the best way to solve this problem.

One of the Sensors Has a Loose or Damaged Electrical Connection

Main Causes of Check Engine Lights
Loose sensor connectors can cause the check engine to light up on your car dashboard. Image source: Club Touareg Forum

Believe it or not, the most common cause of a car’s check engine indicator flashing is due to a poor electrical connection from the ECU to the sensor. If the electrical wiring harness is loose, worn, damaged, or exposed, this can send a signal to the ECU and mimic a mechanical problem. Usually, the sensor will wear out over a long period of time. This tends to happen more quickly with fuel sensors and exhaust systems, which are exposed to hot gases and carbon deposits.

What can be done to fix it? In most cases, a professional mechanic will simply replace the sensor and electrical wiring circuit to solve this type of problem.

Loose or Damaged Fuel Tank Cap

Main Causes of Check Engine Lights
Although it’s just a matter of the fuel tank cap, some cars have a system to turn on the check engine if the lid is not closed tightly. This is good for avoiding the driver from bigger problems. Image source: Rustyautos.com

Today’s modern cars, trucks, and SUVs are monitored very closely for their fuel economy and emissions. If the fuel cap is removed or damaged, or the seal is not secure, the pressure inside the fuel cell will decrease. This alerts the sensor that there is a broken or loose gas cap and could be causing poor acceleration and/or mileage issues. Additional signs of a damaged fuel cap include: The cap is not tightened or locked properly. The car smells like fuel.

What can be done to fix this problem? Oftentimes, replacing the gas cap can solve the problem. However, you should contact a professional mechanic to complete a check engine light check to clear the code and reset the warning light.

Damage to Oxygen Sensor or o2

Main Causes of Check Engine Lights
The third cause of the check engine flashing on your car’s indicator panel is a problem with the oxygen sensor. Dirty or even damaged will cause a check engine. Be careful in handling this problem because there are two oxygen sensors in modern cars. One or both of them having a problem can cause the check engine to be ON.

The second cause of a car’s check engine indicator light coming on is usually part of a series of sensors that monitor the fuel/air ratio and the amount of carbon deposition coming from your exhaust. Since these sensors are exposed to hot exhaust and can be corroded with carbon deposits from fuel and exhaust fumes, they can be easily damaged.

If the oxygen (O2) sensor fails, it can cause the engine to stall, resulting in poor acceleration, poor fuel economy, and more. Failure of the O2 sensor will usually cause the vehicle to fail emission tests in most US states. Other signs of a failed O2 sensor include: Poor gas mileage accompanied by a rotten egg smell Rough engine idle Engine fault is the solution to this problem? Depending on which sensor is faulty, the repair usually replaces the sensor. It is considered best practice to replace all O2 sensors at the same time. When one comes out, the other is usually not far behind.

Clogged Catalytic Converter

Main Causes of Check Engine Lights
Image source: cartreatments

While the O2 sensor monitors the exhaust gases, the catalytic converter is designed to filter the exhaust gases before they exit the exhaust. It converts harmful carbon monoxide into carbon dioxide. Like any filter, the catalytic converter can wear out or become clogged with too much debris to be effective. If this happens, it will generate an error code and trigger CEL. A clogged catalytic converter can cause poor fuel mileage, engine misfiring, and even cause internal engine damage if not replaced. Other signs of a failed catalytic converter are Poor fuel efficiency Slight acceleration when depressing the gas pedal Vehicle refusal to start.

Air Filter or Dirty Fuel Filter

Main Causes of Check Engine Lights
The air filter is very trivial for us to look at. Because it is only a layered work arrangement. It’s just outside the engine. This is far from the main engine parts such as valves or throttle body. But, make no mistake, the check engine can turn on just because of a dirty air filter problem. Image source:Champion Auto Parts.

Regular service and maintenance are essential for your vehicle to operate properly and efficiently. Apart from changing your engine oil and filters every 5,000 miles, changing the air and fuel filters is almost as important. This filter keeps the fuel and air entering your engine clean, which allows your motor to burn gasoline properly.

If the filter gets dirty, your fuel system sensors will alert the ECU and illuminate the dreaded check engine light. Some signs that one of these filters is clogged are: Hesitancy, misfiring, or engine stall Difficult to start or not start the car Performance problems at different speeds Reduced fuel economy. How is this problem solved? It’s simple – replace the air intake filter or fuel filter as recommended by your vehicle’s maintenance schedule.

Mass AirFlow Sensor Broken

Main Causes of Check Engine Lights
I can confirm that if this sensor is faulty the check engine will start immediately. So, check this one sensor for an important step to solve the problem of the check engine on your car dashboard turning on. Image source: WheelsJoint.com

You may see a pattern here. In fact, most of the car’s check engine light comes on due to a fuel or emission system problem. The mass air flow sensor or MAF is responsible for carefully mixing the air to fuel ratio, and maintaining clean and efficient combustion in the combustion chamber of your engine.

If the MAF is faulty, the MAF sensor will send a signal to the ECU to notify you that it needs to be replaced or cleaned. A faulty bulk airflow sensor can prevent your engine from starting. If your car will spin but won’t start, this may be the source. Apart from not starting, other symptoms of a failed airflow sensor include; Engine stops shortly after starting Engine wobbles under heavy loads, and/or when accelerating Engine hiccups.

How do I fix mass airflow sensor issues? This is one issue that a professional mechanic should check first. They can determine if the light is caused by a faulty MAF sensor or just needs cleaning.

The engine has Oil Lubrication Problem

Main Causes of Check Engine Lights

The six causes of the check engine flashing above can be easily resolved in most cases. The seventh problem is a bit more complicated. Your engine needs oil to keep all moving parts cool while working. Sometimes dirty oil, engine sludge, or a faulty oil pump can cause the oil pressure to drop. Or sometimes this causes the increase to be higher than it should be.

If this happens, the oil pressure sensor will alert your ECU and illuminate the CEL. This is one of those situations that we must take very seriously. This is because an engine that does not receive proper lubrication can overheat quickly. As a result, the engine can experience internal engine damage. It could also be that this sensor is damaged and sends false data.

Whenever a car’s check engine indicator light flashes on your dashboard, it’s something you should take seriously. If this happens, don’t wait or assume that it will just go away. This can turn small repairs into large mechanical costs. Call a professional mechanic and have them finish checking the car’s check engine indicator light is on. So they can determine what repairs the car needs to give you peace of mind and ensure your car continues to run strong.

1 thought on “7+ Main Causes of Check Engine Lights

  1. Pingback: Causes Check Engine Turns On Without Symptoms on Chevrolet - Ecotec Engines (Spin, Sonic, and Trax) | Hi-tech for Future

Leave a Reply

Your email address will not be published. Required fields are marked *