2002 intrepid, code p1604

thanks tedmond, i am hooked up to the park lights @ blk / YELLOW at drivers front park light, grounded to dash solid ground frame, tried two diffrent rs modules to bp modules, had pcm flashed, and keep getting code p1604 only during remote start.have two accesory wires hooked up, using the 5th relay wire to power the heater motor.  at my wits end as to why im getting this p1604 code. voltage drop at ground 0.0  if code is cleared and only use factory key, check engine light will not come on. tach signal is from bypass module to rs module, hardwire mode. code only sets once every 15 or so starts. all solder joints are mirror like. all connectors disconnected from modules before soldering. grounds have been clean and tightened.  at my wits ends.