Tatewaki

I got a shock sensor, tried to install it to my OEM alarm. It didn't work I was able to tap into the +ve and ground to have the unit powered up. I also tapped the yellow wire near the E-brake, but after I armed the alarm and move the sensor, nothing happens. :o The LEDs on the sensor are working, but the alarm isn't seeing the trigger. Did I tap into the wrong wire? The one I tapped was a yellow with silver dots. There is another wire near there, but it is yellow w/ black line + silver dots. Is that the one I should tap? Any help appriciated.