I know this isn't exactly hard core, but this is a DD I could use some help on.

My brothers '97 Z71's power steering is acting up. The truck has a lot of miles on it (170+k) and the steering just started getting feather light. At times, it has the right amount of feed back in the stering wheel, then just out of the blue it'll get feather light and have no resistance at all.

The problem started about 2 weeks ago when he pulled the intake off to replace the gaskets (had a vacume leak). There are a couple wires that run from the crank position sensor over to the PS box and terminate there. What are these wires for?

He's checked all he knows to check. The only thing I can think of is the PS box is going bad (stuck valve etc). Anyone else had this experience? What do the wires that plug into the PS box do? Is there some test procedure for the box or whatever sensor is attached to those wires?

Again, I know this is a very newbish question, but I don't know jack about a Chevy and could use some help to get him safely back on the road.

Thanks in advance.

Your problem is with the EVO system. Without a doubt....

Do a google search or look here
http://www.brokentrucks.com/Forum/viewtopic.php?t=5

Thanks for the link, I'm going to do some Google searches on it right now.

According to that post, your suppose to check the OHM's when the key is in the off position and while turning the wheel. Won't the steering column be locked? What he found when looking under there is a small plastic ring that goes around the column. Is that the right part?

That is the part.
I wrote that link so I will have to edit it now. Thanks for pointing that out.

What you would do is unplug the EVO sensor and start the truck. Read resistance of the sensor while turning the wheels "slowly" from lock to lock.
It would be best if you used an analog meter, but most people don't even know what a Simpson is anymore.

Just replace the EVO sensor. That is the problem.

I just unplugged mine, good ridance IMO.

Took mine out along time ago. It gets a little sensitve at 3500rpm but a quick shift to 5th fixes that. :D