Stabilitrak service stabilatrak, engine power reduced, lights come on at start up, and while driving.

SOURCE: Truck losing power and service engine soon light on

Like to other guy said, give it a tuneup. Also try SEAFOAM to clean carb up of slug. Also check to make sure the butter fly for the choke has not come loose, causing it the choke it down. Failed choke pull-off.

SOURCE: 2001 GMC YUKON REDUCE ENGINE POWER ON MESSAGE BOARD

The following is a post from another site. I had the same problem and this worked for me.

Hello all,

I just wanted to share with everyone with the problem that I had withmy 2003 1500HD Crew Cab with 6.0 Liter. My truck would go into reducedengine power off and on. Sometimes one a week, sometimes 5 times on a20 mile trip. My problem was a broken wire on the plug in going in tothe throttle body. In the picture is the plug in that had caused me allof my pain and grief....... My problem was very intermittent and washard to diagnose. I started vehicle and with all codes clear. I wiggledthe wiring harness in the picture and vehicle spit and sputtered,throwing it into reduced engine power mode, and then smoothed out to asmooth idle. I disconnected the plug and pulled wires out of plug endand found a broken wire. Mine was a brown wire with white stripe. BUT,what was interesting, was that this vehicle had apparently had the smaeproblem with previous owner, becuz there was another wire (yellow wire)right beside the one that I found broken already soldered up and tapedfrom where it had apparently happened before. This was my problem andnot my truck is running great, and actually even idles better thatbefore. Hope this helps with any problems that anyone else is having. Iknow this problem can be very irritating.

http://i184.photobucket.com/albums/x191/bunchtst/BrokenWire.jpg

SOURCE: service engine soon and reduced engine power

disconnect batt. for 30 min. then reconnect,if no problem exist the lights will go away

SOURCE: We keep getting a message stabilitrak off, service

I AM HAVING THE SAME PROBLEM BUT MINE ONLY COMES ON WHEN I AM IN GEAR, IDLEING AT A STOPLIGHT OR IN A DRIVE THRU. TOOK IT TO GM AND THEY ARE TELLING ME IT IS A "P0300 AND P0301" CODES WHICH SAYS IT A VALVE TRAIN MIS-FIRE ( TO FIX IT IS A 2000.00 HEAD JOB) AND THAT IS WHY THE STABILITRAK AND ENGINE LIGHT COMES ON!!! IN MY RESEARCH SO FAR I HAVE FOUND NOTHING THAT TIES THE TWO TOGETHER.
I HAVE 102,000 MILES ON MINE AND IT RUNS PERFECT AND MPG IS THE SAME AS THE DAY I GOT IT. I WILL KEEP YOU UP ON WHAT FURTHER I FIND. I AM NOW IN CONTACT WITH THE GM DISTRICT SUPERVISOR.

SOURCE: What does reduced engine power light mean

this model has what they call fly by wire.. no accelerator cable. If the computer detects a problem in the thottle system it will not allow the engine to accelerate and will show reduced power and possibly set a check engine light. The dealer usually wants to replace the throttle assembly which is very expensive and usually un nessesary.
I have had a lot of succes with just cleaning the throttle plates real good.