I drive a 2003 Chevy Tahoe and "Reduce Engine Power" came across my screen for the first time yesterday morning. So I caught the bus to work when I got home I started the truck up and it did not return I rushed the truck to have the oil changed and all the fluids changed or topped off and when I left the truck was running just fine, but again this morning same message "Reduce Engine Power" I allowed the truck to run for about 6-7 minutes and noticed that the truck was idling to about 3 and would drop back down to the line between 0-1 and it continued for about another 4 minutes and I turned the truck off and started and the message was gone again...Please help me