Could these missing temperature sensors be causing the problem?

So after scouring lots of other questions and answers, I haven't been able to solve the case of the snails pace processor in my girlfriend's Macbook Air dual-core i7 (mid-2013). Here is what I know or have tried so far, based on questions from people reporting similar issues.

• When i ran apple diagnostics, it reported error code PFM006 problem with the SMC.
  • I just noticed too that in my system profile, it lists the last diagnostic run as giving reference codes PFM006 and PPN001. I didn't see it say anything about PPN001 when I actually ran the diagnostics, but according to the system profiler, it was both PFM006,PPN001.
• I tried twice to reset the SMC, no change in the problem. Computer still operates at a snails pace, with activity monitor showing that kernel_task is taking up 300% of the cpu. Oh, also i think the fan is running at constant high speed -- but i'm not 100% certain as its my girlfriends computer.
• Booting it into safe mode doesn't fix the issue either, so it doesn't seem to be a third party issue. It still exhibits the same problems as mentioned before.
• I reinstalled Mac OSX (it has Big Sur 11.7.7 running on it). This didn't seem to help anything either.
• I also ran the all disk utility repair options on all the volumes (first aid? repair? i forget the names of the two "evaluate and fix" type options inside disk utility). Every volume I was able to run both commands through to completion, nothing indicated there were any issues or fixes for any issues. I did this while booted into recovery mode. No improvement.
• There hasn't been any liquid spills or anything out of the ordinary that happened to the computer preceding this.

So one of the more promising leads I have found, which I think might be the issue, is that when I downloaded iStats menu and pulled up the temperature sensor dropdown, it has just a "-" listed instead of temperatures for the following sensors: CPU Proximity, Camera Proximity, Charger Proximity, Inlet. Some other people who had similar problems said it ended up being a faulty temperature sensor that was the culprit, which they identified by there being "-" instead of a temp for that sensor, except for them it was the trackpad's temperature sensor. The trackpad sensor seems to be okay here though, reading 75 degrees. Those four other sensors though each read "-" -- could this be the issue?

I am including a screenshot (well, a picture taken of the screen from my iphone) of that istat menu with all the sensors and readouts in case that contains useful information I am simply not able to interpret out of it.

Thank you, in advance, for any insight you can lend!

UPDATE: So after doing some more searching, I think its not necesarily an issue with the four sensors, but rather the BUS they are all connected to. On this page: https://logi.wiki/index.php/Mac_sensors_... I found that those 4 and only those 4 sensors are all located on SMC S0 "1" SMBus -- which probably isn't a coincedence, i'm guessing the problem is probably at least up on that specific level.

So my updated question is this: is this something that I could even attempt to fix myself? I am halfway decent with a soldering gun, but like.. i know if the problem exists within the LCD display there it's simply not gonna happen. I would be willing to try replace a component on the board though. Any thoughts on this would be super appreciated.