Ok so I want an electronic high idle control to my truck and have come to the conclusion I am going to have to make one. So does anyone know how the APPS works and the type of signal it sends to the ECM?

 

mine has a 12v input, with a ground and a signal output of +5vdc to 0.
I'm sure yours is about the same.

 

There are two signal returns to the ecm, do I need to fool both of them or just one to up the idle?

 

put a meter on them and check which has the output from 0 to +5vdc. then check the other wire... it may have the opposite +5vdc to 0 as it's taken from idle to full throttle. It might be that one is simply a seperate isolated ground wire.
wWhat were you planning? Using a solenoid to hold open the APPS cam?
Like the olde style carbs that had a fast idle solenoid that held the throttle open a tiny bit.
I suspect you are trying to use someething like a toggle switch with a load resistor inline to hold a specific voltage vale that corresponds to a certain idle rpm. Or use a variable potentiometer like a volume control and input a variable signal to the ecm to make it think you're holding your foot on the pedle just slightly. Huh?

while you ponder and answer this post, I will look over the schematics for that area and l;et you know what i find out for my truck.

 

ok, here's a page from the manual with the connections. It looks like the terminal shown on the far right is the idle circuit. Good luck.