I could not find any information on D27's ground.Would one of these pins be better to use? This is only a guess, but right now I’m leaning towards using B16. Anyone out there more versed in electronics willing to give me any pointers?
What you could do is set up your logging software and use a battery pack to test if one ground is better than another.
Three AA batteries are usually 4.5-5volts but measure the pack before applying to the PCM.
Can you tell us what output the wideband uses? Is it 0-5 or1-4 or what.
The PCM reading 3.4V instead of 3.5 does not decrease accuracy if it reads the same way every time. What I think you are worried about is losing data range. IE 0-5V is better than if the PCM only reads the widband as 1-4V