Piezo Unlock/Lock Beep in my G1 Prius

Coastal E-Tech seems to have a $40 kit for doing essentially what you want (they use the horn instead of a separate piezo element) ... you could probably adapt that, or study it for ideas.

Cheers,
-Chap

 

I wonder how much of that is implemented outside of the Body ECU itself (the ECU that's built into the fuse/junction box that you see when the driver's door is open). I'm too lazy right now to get out the EWD manual (which I'm sure you have anyway with all the nav hacking you've done), but off the top of my head I don't remember other ECUs being much involved in the Theft Deterrent System. I remember there's a Transponder Key ECU up around the steering column somewhere, but I think that's just the one that recognizes the chipped ignition key and tells the HVECU whether to start.

If the theft deterrent logic is mostly in silicon in the Body ECU, it's not certain you'd find a physical wire somewhere that represents the "flash lights" action. The ECU might just drive the light relays the same way it does when you turn the lights on. You could maybe build a clever circuit with a timer that recognizes the quick flash.

If there's a separate ECU involved but it commands the Body ECU to blink lights via a message over one of the communication busses, then again finding a single wire that represents what you're looking for isn't guaranteed.

But I don't know for sure; I haven't dug out the diagrams to check ... but it sounds as if you have, and judging by your success with the nav retrofits I'm guessing you'd have found the wire already if it were that simple.

-Chap

 

It wouldn't take very much logic to derive what you want. Connect the positive connection of the buzzer to the headlight wire. Connect the negative connection of the buzzer to a relay that connects to ground when the the headlight switch is OFF. The buzzer will sound when the light switch is OFF and the headlight is ON.