2001 Headlights not working with switch.

[JChant]

I have a 2001 Silverado 1500, 5.3L 4X4, the headlights will not come on using the dash switch set to manual operation. No hi or low beams.

The parking lights do work with the dash switch when turned on.

The headlights come on with the ambient light sensor just fine. Hi and low beams work.

Flash-to-pass option works.

Tried 3 different dash headlight switches with the same results.

Tried 5 different relays in the headlamp position in the under-hood fuse block, with same results.

All other fuses in the under-hood block look good with no breaks.

Pulled under-hold fuse block apart and all connectors look clean with no corrosion. No lose wires found.

At my wits end with this. I have the wiring diagram and the only other possible thing I can think of is the headlight relay in the Body Control Module may be the issue, as that seems to be part of the circuit. This type of vehicle wiring is all new to me, and I'm just not sure why the ambient light sensor route and the Flash-to-pass option works, but not the manual switch, if the BCM headlight relay is bad?

I'm hoping someone has worked on this issue and has a fix. I don't want to go the cost of buying a replacement BCM only to find that is not the issue, and I'm starting to think that bypassing all that and running a jumper wire to the headlights may be my only solution.

Thanks all for your time, it is greatly appreciated.