Adjust headlights on 2001 Chevy Silverado Z71

check wires to pump,may be grounded;if not the pump is bad. quite sure its wiring

Transfer Case
NVG 236 and 246 Auto-Trak II Fluid Gm P/N 12378508 NVG 261 and 263 Manual Transmission Fluid GM P/N 88861800

Raise the hood and look for two small screws on the headlight, one is closer to the radiator for side to side adjustment and the other is for up and down adjustment.

Most likely the cable broke, you'll probably have to replace the window regulator.

check your ujoints may have a bad one.

check for a wet tailpipe,which might indicate a leak between water jacket & combustion chamber.i.e.headgasket.check heater hose isn't leaking onto exhaust manifold,'cooking' the anti-freeze as it leaks.

U made need to replace your shocks, doing that made my 01 Z71 stop during that.

There is a light sensor that tells the truck if it is night or day on the dash. Make sure that is it not covered up. If is is not then you may have a bad sensor. It sounds like the sensor is telling the truck that it is night every time the truck is running.

Start the tuck with the park brake on to see if the light come on when it starts. If they do you have a bad relay if not it is most likely that sensor on the dash.

It's the transfer case vacuum switch. Easy fix.

try cleaning your idle control valve, make sure you dont have any codes in your computer, if you do address those codesl