This indicates that a sensor(could be any of many) has either failed or is providing values outside of the normally expected range. The vehicle computer is substituting estimated values for the actual measurements from this sensor to keep your engined running(failsafe mode).

The problem could be minor or serious. Take it to any parts store and have them pull the codes, these should provide clues as to what the problem is. Most parts stores will do this for free.

Check for a service engine soon light if there is none that's what that light means so check the air filter, oil filter, fuel filter and the pcv valve