2001 astro chevy van 4.3 engines need to set the timing

ground distribution center located.????? Doesn't have a center , has ground points - engine block - ignition ?? System ??? coil - module etc.... What engine ???? 4.3 l G-107 & G-105 G107
In the left rear of the engine block next to the knock sensor
G105
In the thermostat housing

Sounds like you timing has jumped. Set the balancer at the 0 mark. take the distributor cap off. The rotor button should be at #1 position or 180 degrees off that. Any other place , the timing jumped.

The power for the data link connector is from a 25amp fuse Number 7 in the IP fuse box. As long as the check engine light is on the computer has power.
The main computer power is from two ECM fuses in the box near the battery.
The fuse locations should be in the back of your owners manual.

THE FIRING ORDER IS AS FOLLOWS : 1-6-5-4-3-2.
CYLINDER NUMBERS (front-to-rear) :
LEFT (driver side) 1-3-5
RIGHT (passenger side) 2-4-6

To set ignition timing, ensure that engine is at operating temperature, (190 degrees or above), bypass EST (electronic spark timing) by unplugging the single tan wire with a black stripe from the distributor. Ignition timing should be set at 0 degrees or TDC (top dead center). If not, loosen distributor hold down bolt and adjust, then retighten.

you either have bad brake pads or the bolts are loose that hold the front steering suspension on.

if the headlight switch does not shut the lights off replace the switch.
unplugging the lights or disconnecting the battery is another option to turn off

You should have a 4l60E in your astro van. Which is electrically controlled, so no vacuum modulator. However, to address the ventilation selector not working... look for a vacuum line exiting the firewall and going to the passenger rear of the intake manifold. You will likely find it broken or disconnected there.

It should be marked on the fuse block

It is located where the big hose comming out of your radiator connects to top of engine. Remove hose from engine your thermostat is undernieth

buy a Honda or Toyota, they work