[Torontofirecaptain]

I just tried something that may be of use to those of you like me, that have more than one 2nd gen with the RKE feature.

I found that a single key fob will be recognized by any number of LH or like cars that use the same key fob simultaneously, so that I now have only one fob for both cars on my key ring. It also remains as 1st or 2nd depending on which number it was programmed in the car, and doesn't affect the program sequence in the other.
The only thing to remember, is that if both cars are side by side. or within 30-40 feet, both will be unlocked or locked when the fob is activated.

 

[IS300M]

so do you have to simuntaneously program each car?

 

[Torontofirecaptain]

so do you have to simuntaneously program each car?

No, I just used one that was programmed for the 300, and tried it in the Trep.
The car accepted it as usual, with me as #1 position.
In the 300 I am #2, and that stayed the same.
Now, with the cars in close proximity, it locks, unlocks, trunk and panic on both similtaneously.
Like I said above, just need to remember that it DOES both if they are close by, so when going out, I'd have to hit the lock after getting in one to relock the other. Minor inconvenience compared to carrying both remotes and figuring which is which all the time.
You do, of course need to reprogram all units for the particular car, since in doing one, it erases all of the other from its memory.