Looking at this further, this is not exactly correct & the link above does work. The relay does work for both the flash and auto lights, but there are two different trigger wires for the relay that merge together. For the flash, you want to disable the trigger from the CSM *before* it merges with the trigger from the light sensor module. That's what the link above shows how to do. That does prevent the flash when locking, but the auto-lights will still work.
I also (finally) got the headlight flash when you lock the doors disabled, without disabling the auto-lights. Turns out that first link provided by MISTERgadget (above) is just what's needed.
OK. Just to beat this *completely* to death...
Here's the deal. Yes, pulling the wire from the CSM as described above DOES stop the headlight flash when you lock the doors.
It also does NOT prevent the autolamps from turning on the headlights when it's dark.
*However*, it DOES prevent all the other lights from turning on by the autolamps. i.e., it gets dark, your headlights turn on, but none of your dash lights, interior switch lights, tail lights, running lights, etc come on.
Note: this is only an issue for using autolamps. Manually turning the headlights on from the switch still works fine.
The wire in question to the CSM works 2 ways. It is grounded internally by the CSM to trigger the headlight relay when you lock the doors. This we don't want.
When grounded externally (by the autolamp module), it causes the CSM to turn on all the associated night time running lights.
So, I cut the wire and inserted a diode "pointing away" from the CSM. Anode to the CSM, cathode away from the CSM. This prevents the CSM from triggering the headlamp relay (when you lock the doors), but still allows the wire to be grounded externally so all the exterior / night lights turn on when the autolamps do.
These were my notes as I was figuring things out. Kinda explains it.
--Dan