A lit check engine light in a vehicle is indicative of one or more problems including faulty oxygen sensors, leaking hoses or manifolds, damaged fuel injector O-rings, a blown head gasket and a loose or damaged gas cap. A blinking check engine light indicates an emergency problem that requires repair.
The most common cause of a lit check engine light is a faulty or loose oxygen sensor. The oxygen sensor measures the oxygen content of a vehicle's exhaust, allowing the computer to compensate with more or less fuel. A loose or missing gas cap is another common cause for a lit check engine light. After replacing or tightening the gas cap, it may take several trips to reset the check engine light.
A blinking check engine light is caused by major malfunctions such as unburned fuel entering the exhaust system or a blown gasket or piston. If the check engine light is blinking, pull over as soon as safely possible and do not drive the vehicle.
Accurately diagnose a check engine light by taking the vehicle to a professional mechanic or auto parts store that can read the code using a specialized device. Diagnostic code readers provide a series of digits and characters that can be used to interpret the exact cause of the lit check engine light.