Interesting problem for you guys.
I have a Viper 5701 installed in an old vehicle (no factory security of any kind). The system has worked great with 0 problems. The vehicle has MES power door locks that I added.
I also installed an Essex AKE-5BH keypad keyless entry system. This is where I decided to get creative (with the inspiration of the12volt.com members in another thread). Because I wanted to be able to use the keypad to disarm the alarm rather than merely unlocking the door (and thereby setting off the alarm when the door opens), I scavenged the number two remote. I busted it open and soldered wires to the lock, unlock, and common traces on the circuit board. These wires run to two relays stuffed inside the door, one for lock, The keypad then actuates said relays. So, in effect, when you lock or unlock the vehicle using the keypad, it is electrically "pressing" the lock or unlock button on the #2 transmitter. As a side note (in case it becomes relevant), I didn't want to have to change the batteries every couple of years, so I purchased a 12V->3V converter for a couple bucks and soldered the output to the battery terminals on the scavenged remote.
This whole system worked great on the bench and once installed into the vehicle. I have had no issues and felt pretty clever for a couple weeks now.
However, something stranged happen.
Last night I had the truck running (using the key in the ignition, #1 viper remote attached to it). I then touched the keypad and entered my code and... nothing. This became particularly stressful because my spare key was in the car. So there I was with my truck running in my driveway, locked out, with no way to get in or shut the vehicle off.
So after I slim jim my way in (and after putting the spare key in the garage :-) ), I shut the truck off. I thought maybe the voltage converter wires had come loose. Everything looked good.
I entered my code into the keypad, alarm disarmed. Tried several times. Everything was working fine.
Started the engine, locked the door, entered the code - nothing.
Any ideas why remote #2 won't lock/unlock while the ignition is on, but will when it is off?