what i can do. my truck turns a light on REDUCE POWER ENGINE on 2003 GMC Sierra 1500

I have turn off the motor and restarting the engine

Asked by for the 2003 GMC Sierra 1500
have codes scanned and post so we can adv
1 more answer
your sensors telling you there is a prob. get diagnostic run to find out what it is. might be easy fix now or big fix later. best to find out.