I have a 2004 Silverado with a 5.3L. I have two problems, not sure if they are related.
First one is when I have driving at a steady speed my RPM raises and lowers about 200rpm. I have been trying to see if the problem happens at a specific point, temperature, etc... but can't find anything.
Second problem is about once or twice a week, the Reduced Engine Power message appears, the truck slows down and I don't have any power, I pull off to the side of the road, shut everything down, restart and the truck is fine till the next time.
Any suggestions?
Oh yeah, the truck has 270,000 miles on it.

Thanks in advance for any help.

 

you probably have drive by wire throttle control; no throttle cable. The problems most likely are related.

With this system any problems with the throttle actuator or pedal position sensor and related wiring will cause the system to enter fail safe mode; which it is doing.

Have the dtc scanned. It may be better to have it diagnosed by a professional.