Nope the PCM controlls voltage regulation.
As for your idle, most Neon's idle at 600-700 RPM and voltage has nothing to do with it.
If you want a higher idle then drill a tiny hole in the butterfly plate on the throttle body. The larger the hole the higher the idle...
2011 Durango Crew - RWD, V6, stock for now.
Former: 2003 Neon R/T: COMP 400 Cam, K&N CAI, Eibach Prokit, Tokico Blues, Hotchkis Sway Bars, Vibrant F/R Strut Bars, Unorthodox UDP, Maddog 72% STS, JonnyMopar Solid Shift Bushings, Prothane MM's, Exel Speeds, Toyo PX4's, RB1 Nav.