Although it's good to know that you probably have an alarm system, you also need to know which one. If memory serves me correctly, it may be up under the passenger dash behind the glove box, or, behind the passenger front kick panel.
Factory installed: 4 button with window button (panic on back). FCC ID = HYQ1512Y
For 1999 1/2. It would be the same
Dealer installed: Model RS3000. And uses a grey remote with no window button.
For 1999 1/2 it might be an RS3200 and a completely different remote.
For the factory fob the Sequoia remote looks the same but different FCC ID
I pulled this information from TSB EL010-01. (OBSOLETE) and was replaced by TSB EL008-02 which I haven't read.
Sorry that I don't have an easy answer but hope this helps.
P.S. It wasn't obsolete on October 26, 2001 when it was published. :thumb3: