ast 1 way fm auto locing doors

Just bought a used 04 Envoy that has a AST 1 way Fm remote, to which I believe is from Ultrastart. My problem is the system seems to be autolocking the doors about 20 seconds after exiting the vehicle. If I unlock the doors via remote.. 20 seconds later it locks them all again. I'd really like to disable that feature. The remote I have is the following

Seems once I interrupt the cycle by cycling the ignition on then off.. then don't lock the doors with the remote it will stay unlocked.. but once I use the remote to lock or unlock it reverts back to auto locking. Still can't seem to figure out how to disable it.

It would be best to crawl under the dash and locate the Ultra Start control module.  It is a little black box about 5" x 4" x 1" with a bunch of wires coming out of it.  On the bottom side should be a white sticker that will have the model number.  It might be something like U3560.  Use that model number and this WEB site to locate the correct Install Manual,  it will have the programming option tables and instructions for making changes :

Ultra Start WEB site :  http://www.ultrastarters.com/manuals.htm  ( It might be in the "Previous Products" section.)

That being said you might have a 35xx system.  Here is a link to that install guide :

http://www.ultrastarters.com/manuals/Prev.Manuals/05_08/MAN-35XX-INSTALL-U-2005.pdf

The programming options table is on Page 15.

Soldering is fun!