* The catalytic converter may be damaged or malfunctioning. The catalytic converter is a device that helps to reduce harmful emissions from the engine by converting them into less harmful substances. If the catalytic converter is damaged or malfunctioning, it can cause the vehicle to fail an emissions test.
* The oxygen sensor may be damaged or malfunctioning. The oxygen sensor is a device that helps to regulate the air/fuel mixture in the engine. If the oxygen sensor is damaged or malfunctioning, it can cause the vehicle to fail an emissions test.
* The fuel injector may be damaged or malfunctioning. The fuel injector is a device that sprays fuel into the engine. If the fuel injector is damaged or malfunctioning, it can cause the vehicle to fail an emissions test.
* The spark plugs may be damaged or malfunctioning. The spark plugs are responsible for igniting the fuel in the engine. If the spark plugs are damaged or malfunctioning, it can cause the vehicle to fail an emissions test.
* The air filter may be clogged. The air filter helps to clean the air that enters the engine. If the air filter is clogged, it can restrict the airflow to the engine and cause the vehicle to fail an emissions test.
