Re: HOW TO TEST PCM
The gauge sweep says possible power interruption and could be as simple as bad grounds or power terminals or low battery.
You are way too quick to suspect the PCM unless you think you have done something to it. Can't really test anyway, the best way is swapping out a known good PCM as there are literally 500 things to be tested there.
You will get zero through the comm port with just a single bent pin to not make connection. Just went through that at inspection, the loser running the place told me my PCM was 'bad', LOL. Nothing wrong except for the 3 rolls of electrical tape he had wrapped around the OBD connector of his cord, that tells you everything.
Noise from fuel tank may be telling you the pump is bad, they can be heard to spin up and still be bad, the difference is HOW they spin up, you listen for the subtle little difference that says it's not working like usual. Could be partial power from your gauge sweep issue too, pumps get wonky at low volts. You may not get PCM communication if the voltage to it is off as well.
Need to be going after battery WAY before PCM, it being low can blow your mind with various oddball errors. You need to verify both battery and alt charging, they could be fooling you................need at least 12.3 volt or more at battery.