I figured someone on the internet had already explained it better than I could, so I hit up Google and here is one response that seems to make sense. I realize it is for a completely different model, but I'm assuming it works similarly on our trucks.
http://www.cadillacforums.com/forum...position-sensor-what-does-do.html#post2983883
The Steering Wheel Position Sensor is just that: it senses wheel position and wheel turning rate as one of more than a dozen body and drivetrain sensor inputs to the active suspension, stability, and ABS systems. There is also a magnetic function which increases steering wheel turning effort required as vehicle speed increases - at high speeds there is practically no power steering function. It is wrapped around the lower steering column and requires column removal for replacement.
Chris, I checked in GM Parts Direct and found p/n 26084178 for my 2001 Yook. Googling that number, I found another GM listing that broke it out in more detail and listed it for 2002+ models. I decided to look how these sensors work and what they do. I couldn't find anything specific to my truck but found this info in the following forum:
http://www.gmforum.com/2000-2005-90/steering-wheel-position-sensor-225179/
"You've got basically the right idea,but there'* quite a bit more to the Stabilitrac System............along with the ABS system(to detect a wheel losing traction),.the steerinng wheel position sensor works in conjunction with the stability sensor(a lateral accelerometer located at the center of the car[I know in the Grand Prixs it'* under the center console between the seats]),......when the two sensors detect a discrepancy between the direction you are steering(steering wheel position sensor)and the direction your car is Actually going(lateral accelerometer) it kicks in the Stabilitrac.........and depending on whether the car is oversteering (rear wheel losing traction during a turn/curve,causing the back of the car to 'spin out') or understeering(front wheel losing traction during a turn,causing the car to 'plow through'/miss a curve) the Stabilitrac System will apply braking to Either the outside FRONT brake(in oversteering) or the inside REAR brake(in understeering)."
I think now that there is no steering position connection to the PS system in my truck but to the ABS and possibly the traction control system. I don't think I have a "Stabilitrak" system per se but it does have traction control. I know this works as I punched it going up a tight right-hand rising off-camber turn in the rain and it hooked up and just went.
I went back and looked at the GM Parts Direct listing and realized that is where I found the 2002 reference. If you expand the application for GMC Yukon XL 1500 you will see that 2001 is not listed although the page does say its for 2001 under Product Description. Confusing. eh? Here's the link:
http://www.gmpartsdirect.com/gmc/yu...eering-column-****/?part_name=position-sensor
