I looked through the forums and I found some information [capp777] about calibrating the Adapter voltage. My 97 Toyota doesn’t report command module voltage and I only get it from the adapter, which works but my vehicle also has notorious voltage drop in the wiring and Im trying to find a reliable method for battery voltage. I know the difference between the reported adapter voltage and the open circuit and closed circuit battery voltages as measured with a quality Voltmeter. What I am looking for is a way to use this information to calibrate the adapter voltage is display closer to the actual battery voltage.

I went through the forum as best I could but I couldn’t understand a lot of it, including sending an ODBII command. Is there a way to do this? Either through changing the built in PID or creating an external one?