There is fun frustrating thing I figured out with the GM upfitter diagrams. If they feed two same color wires into the same Pin location on a connector, Ex- BCM X2 pin 5 has two VT/GN wires the Diagram lists only 1 wire( two different colors are always listed on the same Pin). One feeds the puddle lamp under the mirror and the other feeds the electric step lights.
On 2020+ 1500s and 2024+ HDs the BCMs are different.
Look at the K219 Lighting Control modules - X5 Pin 1 or Pin 4?
-Puddle lamp control
- exterior Courtesy lamp control
-Front footwell accent lighting
Then you can unplug the 2 wire connector feeding the step lights and use a wire tracer, power probe, or continuity test with a multimeter to confirm the control wire.