2006 Tucson V6 PO123 High Voltage at Idle

My 2006 Tucson V6 Engine lost power on the road and RPM's went down and then up. Engine idled at around 700 RPM. Currently getting a reading of 3.75 Volts for Idle at the disconnected TPS Harness connection. Replaced TPS and now the engine idles at 4000 RPM. This is probably understandable since I'm getting 3.75 Volts at the Harness. I don't know what is causing the excess voltage. I thought of checking the Voltage from the PCM to see if it was putting out the 3.75 Volts, but I don't know where the PCM is located. There is a box under the passenger side seat which may be the PCM. I'm an 80-year-old Retiree with Basic Tools and a Six Dollar Volt Meter. I would prefer to trouble shoot the issue myself if possible unless it is absolutely necessary to take the vehicle to a Dealership. So, where do I begin the trouble shooting?