If your vehicle is showing check engine light stays on, here are the most likely causes and the parts you'll need to fix each one.
A loose, missing, or damaged gas cap allows fuel vapors to escape, triggering an evaporative emissions (EVAP) system leak code. This is the most common and easiest fix for a check engine light.
Oxygen sensors measure the amount of unburned oxygen in the exhaust. Over time, they become coated in combustion byproducts and fail, leading to poor fuel economy and an illuminated check engine light.
Worn spark plugs or failing ignition coils cause engine misfires. This will trigger the check engine light (often flashing if severe) and cause the engine to run rough or hesitate.
The MAF sensor measures air entering the engine to calculate fuel delivery. It can fail, get dirty, or frequently be left unplugged by mistake after checking or replacing the engine air filter.
The catalytic converter reduces exhaust emissions. If it fails or becomes clogged (often due to ignoring misfires or bad O2 sensors), the check engine light will illuminate with an efficiency code.
These valves control the flow of fuel vapors into the engine to be burned. When they stick open or closed, they trigger an emissions code and can sometimes cause difficulty starting the car after refueling.
VVT solenoids adjust camshaft timing based on oil pressure. Dirty oil, low oil levels, or a failing solenoid will trigger timing-related engine codes.