If your vehicle is showing check engine light is on, here are the most likely causes and the parts you'll need to fix each one.
A loose, damaged, or missing gas cap allows fuel vapors to escape, triggering an EVAP system emissions code. This is the most common user-induced cause after refueling.
O2 sensors degrade over time and get covered in carbon or oil, causing incorrect fuel mixture readings. This reduces fuel economy and triggers the light.
Worn spark plugs or failing ignition coils prevent the air-fuel mixture from igniting properly. This causes a misfire, which often triggers a flashing check engine light.
The MAF sensor measures air entering the engine. It can fail, get dirty from neglected air filters, or trigger a code if accidentally left unplugged after an air filter replacement.
The catalytic converter reduces exhaust emissions. It usually fails because a bad O2 sensor or ignored engine misfire allowed unburned fuel to overheat and melt its internal honeycomb structure.
Valves that route fuel vapors into the engine to be burned can stick open or closed. This causes an emissions leak code even if the gas cap is tight.
Sludge buildup from infrequent oil changes can clog the VVT solenoid, preventing it from adjusting engine timing properly and triggering a code.
If the thermostat is stuck open, the engine will not reach its optimal operating temperature fast enough, which the computer flags as an emissions issue.
The main vehicle computer can fail due to voltage spikes, water intrusion, or internal short circuits, causing persistent or erratic check engine lights.