Remote starts using "tach sense" look for a voltage level to be reached on the tachometer wire. The wire uses AC current, not DC. When that range of voltage is reached, it ceases to crank. This also allows you to press your remote start button when the car is already started and then remove the key and leave the car running when you want to run in somewhere. I worked at the local stereo shop for almost 2 years and installed several alarms/remote starts.