[06GMC5.3L]

Parked the truck for the day this morning. Been cold all day around 10°. Got in it this afternoon started it up with reduced engine power message. Shut down and restarted a few times finally the message went away and I was able to drive home. First time this has ever happened. Didn't get a chance to have the codes read yet.

Any ideas?

 

[GREENSIERRA]

Check the codes when you get a chance, it will really help narrow it down
If it happens again before checking codes try wiggling and pulling the wires going to the TB

 

[06GMC5.3L]

No message this morning.

 

[WillyPaul]

Apparently GM has had lots of issues with this. Just google reduced engine power. Mine did it for the first time in december. It went away, I kind of forgot about it and now it just happened again last night. I just watched this video and was on my way out to check my connections when I found your thread, so hopefully this helps. Most everyone seems to have the same experience of ignoring it at first, it'll be fine for a while then come back.
https://www.youtube.com/watch?v=U2DjMcM_Quk#t=427

 

[2005_Silverado]

Probably a stuck throttle body blade