Originally Posted by fuddyduddy121
Well, I could draw the electrical diagram, someone would have to QA/QC it, and then we would need someone to carry out the experiment on their car.
I guess all you'd need to do is tap into the voltage pulse to the door lock (two, actually: one on the Unlock side; the other on the Lock side).
Only trouble with that is that I don't think the pulses are very long, maybe not long enough to hold the relay closed long enough to really light the bulbs.
Aftermarket keyless-entry systems can do this, but their processors use a separate pulse to the lighting circuit that (I believe) is deliberately longer duration than that to the lock system, so that the bulbs have a chance to come up to full brightness.
The key lock in the door contains wires to the Lock and Unlock circuits so that you can control all doors (and the filler cap door) via the key, but those operate by grounding one circuit or the other, not by energizing it, so you could conceivably also tap your light-flash relay in there, but your wiring would need to be a lot more creative.
I think it might be easier in the long run to just get yourself an aftermarket Keyless Entry kit that can flash the lights like you want. As long as its Lock/Unlock connections are made to the Lock/Unlock wiring at the outside door key lock, you'll still be able to arm and disarm the factory alarm system via the aftermarket Keyless Entry kit.