Factory keyless entry signal relay
 

Long shot here, but curious if anyone has intricate knowledge of how the factory keyless entry works. I have a 99 limited and initially I was able to program a remote but now the truck will not go into programming mode despite installing four brand new lock actuators.

Dealership says it's an "internal signal relay" and would be very expensive. Does anyone know anything about these things? I'd like to avoid aftermarket if at all possible, and would like to fix the factory system.

I think it's coincidence but I *did* install a new head unit and maybe spliced a wrong wire? My head unit correctly dims off the factory harness, and powers the stock antenna as well. Not sure if they're tied together or not...

Thanks in advance for anyone's help.