The check engine light on a Ford Ranger, or any other vehicle, can indicate a variety of problems, ranging from a loose gas cap to a faulty catalytic converter. Occasionally, the check engine light comes on because of a change in humidity or other environmental factors.
A mechanic can diagnose the problem that caused the check engine light to come on. In 2010, some of the most common reasons for the check engine light to illuminate were problems with the mass air flow sensor, the O2 sensor and the spark plug wires. A flashing check engine light indicates a more serious problem, and it is best to have the vehicle checked promptly.