Replace original horn with Lexus LX600 genuine horn

Not sure what yours looks like, but if they're anything like the FIAMM horns I upgraded to, there should be some short black wires included with each horn. They have a push on terminal on one end, and a ring terminal on the other end. Use this wire to ground one of the two male terminals on the horn to the mounting bolt/bracket.

Then connect the other male terminal on the horn to the female oem connector from the car wiring harness.

So, in short, your horns weren't grounded properly.

SM-G781V ?

 

Not grounded properly

 

Does anyone know which side the 500hz vs 400hz goes to?

 

Doesn't really matter.

SM-G781V ?

 

I got my box from China yesterday (Lexus/Highlander horn kit) and got them in today....2021 Toyota Prius AWD. Just required removing the top black cover over the radiator area, didn't have to remove the front grill/bumper. Before I installed the new horns I plugged them in and tested them to see if they worked....NOTHING! What?? Then my engineer brain kicked in and said, "needs to get connected to the car, ground it dummy" And, yep, both are working and MUCH louder.

Some tips for y'all:

-Definitely will need a 12mm ratcheting wrench....very little room to get to the one bolt, especially on the left side.
-You just unplug the connector from the old speaker and then remove it with the bolt on the FRONT of the car frame....you can leave the other 2 or 3 alone.

The kit come comes with a new connector but didn't need to use it....it also has new 12mm bolts and zip ties...didn't need any of it.

 

I also just did mine the other day(I've had the kit for something like a year). And I also did the same thing you did by plugging it in and being confused why it didn't immediately work. Only when I took a close look at the plug and realized it was single pin did I begin to realize my issue. lol

(I made it worse by messing with the adjustment screw before installing. I didn't realize what it was for and tightened it down to the point it stopped the membrane from working. Once I loosened them, I got my nice, loud, two-tone horn. )