Next step:
Remove both high beam bulbs, (leave the low beam bulbs out). Measure resistance on the yellow with black stripe wire between left low beam and left high beam sockets. Same way that you did in the last test, terminal to terminal. Same thing, checking end to end of the yellow with black trace wire this time. Leave the light switch and ignition OFF.

 

Ok on the left low beam there is a Solid Yellow wire and a Solid Black wire. On the Left High beam is a solid Black wire and solid purple wire.

 

Hmm, the schematic shows different from what you found. It says "information not available" for the left high beam positive. No black wires on any headlamp socket. Let me study it for a minute and figure it out. It might tie into the DRL relay, give me a minute.

 

Just for grins and giggles, check resistance, (end to end) on the black wire between the high and low beam sockets.

 

Okay speaking of the DRL.

Observation #1
With the DRL plugged in
* Passenger side high beam (DRL) is on.
* Driver side high beam (DRL is on)
* When lights are turned on, the passenger side low beam is on, passenger side high beam is dim and both driver side low and high beam is dim.

Observation #2
With the DRl unplugged
* Passenger side high beam (DRL is on) No driver side lights are on.
* When I turn the lights on the passenger side low beam is on and the passenger side high beam is not dim and on the driver side both high and low beam are not on.

Flash to pass (high) only operate High Beam bulb on passenger side. Something is up with the driver side.

I bought low beam connect to replace the driver side if I need to go that route in troubleshooting a bad driver side connector.

 

The possibility exists that when you checked resistance, and got the 1.2 ohm reading, you may have wiggled the socket enough to have it make good contact. That is definitely a tough one to diagnose, almost easier to replace the socket and see what happens. Or, plug the bulb in and wiggle the two wires close to the socket and see if it makes a difference in bulb intensity.

 

Passenger Side Low Beam
Yellow Wire
Blue Wire

Passenger Side High Beam
Purple Wire
Green Wire

Resistance was like 0.8

 

What are the colors and locations of the wires on the driver side? Something stupid with this schematic. It's a genuine GM publication for 2000 S&T series, but something is screwy. Your right side low beam matches the schematic, yellow and dark blue. But right side high beam shows purple and dark blue.

 

Driver side High Beam
Solid Purple
Solid Green with a white strip

Driver side Low Beam
Solid Yellow
Solid Yellow with a black strip

 

Scratching head..... just to make sure we're on the same page here... the outboard bulbs are the low beams. The high beams are inboard, (closer to the center of the vehicle). The DRL's operate the high beam bulbs at 30% intensity. At least that's how it should be. Are we together on this?