something happened to trigger the oem anti theft. not aftermarket. but for future reference, if there are issues with the remote start, simply get under the dash and remove it. theyre much easier to uninstall than to install. just make sure to tape any bare wire once finished. being an 01, it would have required a transponder override, and if not properly installed, or properly programmed it can cause some serious issues with start up or security--also inserting an incorrect key and attempting to start the car can cause a starter interrupt pattern in the car. look for either an ignition cylinder ring or to see if someone has tapped a programmable bypass into rx/tx data wires where the key inserts (under the plastic around the ignition cylinder). its always fixable, just a matter of getting the wiring correct, or potential programming.