Due to the fact that I couldn't find any info about this on the net, I decided to post the following instructions in case any newbies are looking to do this.
Newer Subaru vehicles disable the factory keyless entry when the engine is running or the key is in the ignition. This modification will allow you to utilize your factory keyless entry remotes if you are installing an aftermarket Add-on remote start type system. This will only show how to MOD your existing keyless system to allow the transmitters to function while the engine is running. This won't show how to install the remote start system itself. This MOD was done on a 2003 Subaru Outback Wagon
On this vehicle I added a DEI add-on starter that is triggered by 1, 2 or 3 consecutive lock pulses from the factory transmitter. I used 3 pulses because I wanted to hear the horn honk once before remote start. The DEI unit can be set to 2 pulses if you don't want the horn to honk. The horn honks on the factory set-up after 3 presses because that is the car finder feature from Subaru. To shut down the starter via remote, only 1 lock pulse is required. Unfortunately if you don't MOD the keyless system you will not be able to provide the lock pulse to shut down the system if there should be a problem. Also when you approach the vehicle and try to unlock the doors via remote, you would not be able to because factory keyless is disabled by the ignition power.
The 2 wires are and GREEN / WHITE (Ignition sense) WHITE/ Green (Key sense).
I decided to put the photos on yahoo.
Some instructions are below each photo.
Keyless while Engine is running
If that link doesn't work use this
There are also a few pics with the ECM tach location
and the integrated module's remote start activation lock pulse wire location
Remember that using the existing sytem to trigger your remote start system will limit your range. The typical range of the factory system is usually about 30 feet or so. If you are looking for a longer range then you may want to install an aftermarket remote starter that has keyless entry integrated into the unit. These typically have a range of about 500-2500 feet depending on brand/model.
note** The keysense was disabled to allow the pit-stop function to work on the remote start unit. Pit-stop means when you arrive at a store or something and you want to keep the engine running. You would be able to activate the start unit by pressing the lock button on the keyless remote. If you leave the keysense wire uncut then you would not be able to use the lock button while the key is in the ignition. This would mean you would have to turn the engine off and remove the key before you could activate the lock button 3 times to trigger the remote start to take over. Cutting the keysense allows the function to work but I think it may disable the ability to learn new remotes to the system. You may choose to put a toggle switch on the wire in case you ever need to reprogram lost remotes. Or you could just leave the keysense wire intact and not use the pit-stop feature.
Thanks, Steve G