Five Common Check Engine Light Causes:
Loose Gas Cap
Fuel vapors leaking out and can imbalance the fuel system.
When this fails it reduces the sensors ability to change the oxygen fuel mixture. A faulty sensor reduces your gas mileage and increases emissions.
In theory shouldn’t fail if regular maintenance is kept up (i.e. replace spark plugs and failed O2 Sensors). Symptom of a faulty catalytic convertor is poor gas mileage and won’t accelerate.
Mass Airflow Sensor
Usually fails because air filters are not replaced regularly. Function of the Mass Airflow sensor is to tell the car’s computer to add the proper amount of fuel based on the air coming into the engine.
Spark Plugs and Wires
A maintenance that should be done to prevent potential check engine lights and failed smog.