2003 Chevy Trailblazer w/keylees entry

I'm installing a keyless upgrade(siren,flashing lights and shock sensor) in a 2003 Trailblazer.Judging from what I've read here,I'll have to go into at least one door for the lock & unlock wires to hok to the upgrade module.

Does this sound correct?

Thanks.

You'll need to do a reverse polarity in each door and the tailgate as well.  For the rear doors you'll find 2 relays on the BCM  under the rear seat, send a negative pulse on each pin 85 to make the rear doors work with all other doors.

OR

You can order a module that you hook 1 wire up to the data connector and it will take care of it all for you.

I highly recommend option 2 :)

Thanks to all...I guess I didn't make myself too clear in the initial post....the factory keyless entry is going to stay in the vehicle....so option 1 would not be necessary...doing option 2(and swapping remotes) sounds interesting,although I'm not sure the upgrade module comes with remotes.

Anyway,thanks again.