Help with Lynx 2000 factory disarm

I have been trying to get the factory disarm to work with a Lynx 2000 on a '02 Silverado. When I connect everything I cant get the factory alarm to disarm. I even traced all the way back to the drivers door unlock switch to make sure I have the correct lt. green wire.

The Lynx book says it sends a negative pulse on the disarm wire, but when I hook it do a DMM it measures a constant -12 when the system is disarmed and goes to 0 volts when the system is armed. It doesnt pulse. Is this correct or do I have a bad module? I am using the GREEN/ black wire on the Lynx with a diode (cathode facing factory unlock).

Any help would be greatly appreciated.

Thanks.

Thanks David -

Is there a way to change the Lynx to a pulse output. The book says it is pulse by default, but that isnt whats happening. The book also says you can program it via the remote, but doesnt tell how to program it. I have been thru all of the other programming modes and cant find anything in the programming mode for this.

Im running out of ideas short of using one of the aux connections. The book does explain how to change those to pulse output.