Engine Light on. Dealership says fan clutch is Slipping

No! there is nothing to reprogram. The sensors in the coolant system and the temp sensor for the fans dont need to have anything done to them. If you are not getting any check engine light, you are good.

Motor relay circuit this is for the ABS, you will need ot restore the third eye brake light and check fuse in the engine junction fuse box, (cigarette lighter fuse) make sure it didnt open

I have the same car and the same problem.......

Service Engine Soon (SES) or Check Engine Light On, DTC P0480, P0526/P1481/P1484 Set (Replace Engine Cooling Fan Wiring Harness) #05-06-02-012B - (10/19/2006)

Models:2004-2006 Buick Rainier
2002-2006 Chevrolet TrailBlazer, TrailBlazer EXT
2002-2006 GMC Envoy, Envoy XL, 

Some customers may comment that the Service Engine Soon (SES) or Check Engine light is illuminated. This condition may be intermittent and upon investigation, the technician may find either DTC P0480, P0526, P1481 or P1484 set.

This condition may be caused by the cooling fan harness chaffing against the plastic guide it routes through. This contact may damage the insulation of the wires enclosed in that harness.

Replace the wire harness: 
Part Number 89024920 Description Harness Assembly, Engine Cooling Fan Wiring

Good luck and keep me posed. 

Clicking sound- Possible electronic fan clutch failing. This is a typical problem with the 4.2L I6. When you hear the clicking, open the hood and listen if its coming from the fan clutch on front of the engine. this could also cause abnormal engine and transmission cooling. As for the "N" light and 4wd issue, have scanned at the dealer....Hopefully this helps

It is in the front of the engine with the fan mounted to it. It is electronicly controled. If you change it be very careful the radiator is easy to damage. Good Luck

the fan relay is bad

I would guess it is the electronic fan clutch. It will cause the fan to run too fast (very loud) and the light will come on sometimes.

You need to find a shop with a Tech 2 scanner. The pcm has to be recalibrated because when the fan clutch goes bad it back feeds into the computer and stores a hard code. And because the 02 is the first year for this style envoy its a pos! And these A**Holes from GM thought it was a good idea to have a electronic throttle body and gas peddle.

So in a nutshell it needs to have a PCM.AZ UPDATE AND YOUR DONE! SELL IT AND BUY SOMETHING YOU CAN FIX IN YOUR BACKYARD ON THE WEEKEND!

I ran into this concern with my 2002 and my wife ran into the almost identical problem with her 2003. this may sound silly,, but it was the clutch fan. Extreme loss of power from time to time came first. Then a roar of the what seemed like the engine when stopping. Actually cut off after it started to roar at highway speeds, and had absolutely no excelleration from time to time. Sometimes all of the symptoms completely went away. After taking mine to the dealer several times, finally they got it right and replaced the fan clutch. When my wifes 2003 SLt started doing the exact same thing as my 2002 had done, we both knew what the problem was, and the dealer did a quick fix. $600.00. Perhaps this should have been a recall feature, but never was. Everyone that I know that has an envoy, somewhere around the 72,000 and 103,000 mile mark has had this problem and have had to have the clutch fan replaced. It may sound like the vehicle is going to have to be junked,, but that is all it needs.