This is incorrect. Lots of '99-'02 trucks, including mine, came from the factory with no alarm/security system but WITH wireless door locks. (Some late '98's as well.) That system used the HYQ1512Y four button remote: Lock,Unlock, Rear Window plus Panic on the back. The factory system 'brain' is built in into the Body ECU and the wireless receiver into the Back Door ECU. The only visible evidence is the chirper doohickey on the passenger fender in the back corner almost to the firewall. It looks like this:
If you have the LED security light in a 2000+, that may be the factory system with alarm or it may be the RS3200 which is NOT factory. Those were dealer or port-installed options, but they still use the same HYQ1512Y. (1999 and earlier alarms were the RS3000--also port/dealer ONLY--and used either the grey or black 2-button remote depending on year.)
Bottom line,
in a 2002: First see if you have either the chirper or a security LED, then get the black 4-button HYQ1512Y fob. It works with all three systems: factory wireless with or without alarm, and add-on RS3200. There were other versions on other Toyotas that look the same with different FCC numbers--those won't work.(Stay away from ones with a trunk lid on the third button unless you are sure of FCC number--you want the one with a rear window.)
See Toyota TSB attached: