Circuit feed is from Fuse 1 Stop/Haz 20A on an 8 Ga ORN wire to TCC Brake & Cruise Control Release Switch (Brake Switch ??). Out of TCC on an 8 Ga WHT wire to S228. Then from S228 to C215 on an 8 Ga WHT wire to S405 on a 16 Ga WHT wire to lamp.
Please note that there is a 510 ohm 1 watt resistor in parallel with the lamp in this circuit.
This info is from the schmatic for a 97 Jimmy, but I don't see why this circuit would have changed for your 2000.
Remember the best way to check this is with a DMM and start from the ground end and work your way back to power.
Post back and let us know how you make out in repairing this.