GMC Denali

There should be a button on your truck that looks like a truck sliding or swirving. Press the button and traction control off should appear on your dash.

Check all connectors for moisture and dry them out.

measures the ambient air temp (outside air temp) and sends that info to the computer to adjust air/fuel ratio for best burn.

Pop the hood, look right at the top and back side of the headlight casing to locate an "L" shaped piece of steel. Turn it 90 degrees (left or right depends on which side of the car you are on) then after you turn it, it should either pop out of place or slide straight up and out of position. once you've done that, the headlight casing should come out as one piece. on the back of it there should be a center point where wires go into a plastic base, twist that base 90 degrees and it too will pop out, thus exposing the light bulb. bulb comes out and is ready to be replaced with HALO bulb :) after this, be sure to put everything back in order and if you have leftover parts, you missed a step.

Dex-cool

the one on my 04 silverado cost 2200 CDN, so about the same I would think.

simple a hydro boost system,will be plumbed to the power steering unit .... it receives turning force from hydraulic power.... a vacuum boost simply gets power from the intake manifold. most hydro type systems found on 4x4 and commercial grade vehicles

turning force is wrong .....stopping is right word....other wise correct

Find where the compressor assembly is on your vehicle. Unplug the connector with all wires. Set your DVOM to ohms and check the resistance on the compressor side of the connector of the light blue wire and the gray wire..... it should be 18-45ohms. That is the exhaust valve solenoid which the computer throws code CO660 when it's bad. There's no repair for it, just replace the whole compressor assembly.

if you diagnose the GM by GM MDI, you can repair it or reset by some obd2 code scanner from vipprogrammer.com

Yes