Connect the outputs at the BCM (or keyless module) to a relay (or relays) and then to whatever you want to turn on. It's more complicated than you think.
Probably the easiest and least destructive would be you use 3 relays.
30A SPDT Relay 1
Terminal 85 to ignition
Terminal 86 & 87a to ground
Terminal 30 to relay 2
30A SPDT Relay 2
Terminal 85 12V horn signal (at horn)
Terminal 86 & 30 to Terminal 30 from relay 1
Terminal 87 to relay 3
30A SPDT Relay 3
Cut supply wire going to the light
Terminal 85 & 87 to 12V Batt FUSED
Terminal 86 to Terminal 87 from relay 2
Terminal 30 to light side 12V of the cut supply wire
Terminal 87a to the switch side of the cut supply wire
Relay 1 passes ground to relay 2 so when the horn is honked, relay 2 can send ground to relay 3. However, if the ignition is on, relay 1 will not send ground to relay 2 so the lights won't flash if you hit the horn while driving. Relay 3 allows voltage to pass from the switch to the light while at rest. When relay 3 gets a ground signal from relay 2 it sends +12V to the light and not back to the switch; essentially acting as a diode.
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2006 CRD
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