Ford Fusion Check Engine Light Diagnosis | Cost & Service

Publish date: 2024-06-05

6 Reasons Why The Check Engine Light May Come On

Here are the six common reasons that can trigger the check engine light of your vehicle: 

1. Loose Gas Cap

Sometimes, an issue as simple as a loose gas cap can cause the onboard diagnostic system to turn on the engine light. 

Your gas cap is part of a sealed evaporative emissions system that prevents the gas vapors from escaping into the air. If you accidentally leave this gas cap loose, you can lose fuel through evaporation, and your exhaust gas recirculation system will not function smoothly.  

2. Failed Oxygen Sensor

An oxygen sensor measures the unburnt oxygen in your vehicle’s exhaust system. This helps the ECU to know how efficiently the fuel burns during combustion. Accordingly, the ECU creates an ideal air-fuel mixture to offer optimum fuel economy under different driving conditions.

However, these exhaust system sensors have to tolerate extremely high temperatures and are prone to fail when your vehicle crosses 80,000 miles. 

A faulty oxygen sensor can even damage your spark plugs and catalytic converter, leading to costly repair. Your vehicle will also not pass the emission tests as a bad catalytic converter will release harmful compounds like hydrocarbons and nitrogen oxides. 

3. Weak Car Battery

When your car battery is weak or isn’t fully charged, it’ll fail to send enough power to your vehicle’s ECU. This will result in an illuminated check engine light, and your ECU will register a diagnostic trouble code (DTC).  

You may also notice an illuminated battery light on your dashboard, indicating an issue with your battery or alternator. When that happens, you should call your service center and schedule a battery service. 

4. Faulty Spark Plugs

A spark plug generates an electric spark to crank your engine. When the spark plugs are worn out, they can lead to ignition problems, reduced fuel economy, and even damage other essential elements of your vehicle.

Bad spark plug wires can also cause a flashing check engine light. In other cases, it could be the ignition coil that’s to be blamed. 

5. Engine Misfire

Spark plugs help ignite the air and fuel mixture in the combustion chamber. If the timing of the spark is off or if the fuel mixture and its compression isn’t right, your vehicle can misfire. 

Some other reasons that could also cause an engine to misfire and trigger the engine light are: 

If you keep ignoring the check engine light for engine misfires, they can result in severe problems like a mechanical failure of your car’s engine.

These failures can be pretty heavy on the pocket if your mechanical breakdown insurance doesn’t cover it. 

6. Faulty Mass Airflow Sensor 

The mass airflow sensor in your vehicle measures how much air enters the engine. The ECU uses this data to determine the amount of fuel to inject into the combustion chamber. 

If the sensor goes bad or there are any leaks in the air intake tract, you’ll notice an illuminated check engine light. 

The mass airflow sensor is also sensitive to dirt, water, and oil. So, contamination in the air tract can trigger the check engine signal too.

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