1999 Ram 2500 P0505 Code: Parasitic Draw and IAC Solenoid Power Issue

Hi, I'm Geoff and I own a 1999 Dodge Ram 2500 with a 5.9L V8 engine. My battery is consistently dying overnight, and after troubleshooting, I've identified the issue as a parasitic electrical draw originating from the ECU circuit. Using my OBD-II scan tool, I detected a P0505 code — indicating an idle air control (IAC) system malfunction — but there's no check engine light illuminated. To test this, I disconnected the IAC solenoid connector and observed that the parasitic draw dropped from 0.300 milliamps to just 0.070 milliamps, confirming the IAC as a likely source. When the ignition key was off, I measured 8 volts on one of the IAC solenoid plug terminals — which is concerning because there should typically be no power to the IAC when the engine is off. My question: Is it normal for the IAC solenoid to receive power with the key off? I can't find any official documentation confirming this behavior. Has anyone else experienced a similar issue on a 1999 Ram 25 or 5.9L V8 model? Possible causes include: - A faulty engine control module (ECU) - A short in the wiring harness - A defective IAC solenoid Any insights, experiences, or technical references would be greatly appreciated. Thanks for your help!