It sounds like wiring or ground issues. Especially, since it's intermittent.

I would start with the easiest first. There is a plug in front of the transmission that goes into the TCM. These are notorious for having loose pins. So I would start the car and then reach down and move that plug and wiring around and see if you can hear the motor change sound, or have someone sit inside and see if any warning lights come on while you move that plug/ wiring.

Then I would unplug that connector and look for any burnt spots, or corrosion at the connector. I would take some electrical contact cleaner and spray the plug and then the female side of the TCM connector as sometimes they get Transmission fluid in them and can cause ghosts.

Next I would check all grounds you see. Either test them with a multimeter or better yet undo each one, take a small wire brush and clean them and put them back together. There is a series of grounds on the driver's side radiator support. There are like 3 and then one on the body frame down below. I had a bad ground at my TCM and I cleaned all those and it seemed to fix it. I'm not sure which ground did it, but after cleaning them all it seemed to fix it.

I would check the car battery and battery terminals. When you have a failing battery or corroded terminals it will cause intermittent problems such as this. I would pull the battery out, clean the terminals and then take it into an auto store to get tested. Replace the battery if it is worn at all.

Since almost all your codes are at the TCM, I suspect it's a loose wire/ faulty ground/ oil in plug to the TCM, or a faulty battery. Or a combination of the two.

I would start there and see then if it fixes your ECM/BCM code.

Btw, I would really check your power from fuse #1 in the fuse block to your TCM. It's plug #10 in this drawing. Hook a multimeter, or test light to the negative terminal on the battery and check fuse #1 in the fuse block and make sure you have power on both sides of the fuse, then test terminal #10 on this plug to see if you have the same power. If at the fuse you see say 12.4V, then that #10 in the pigtail should also be 12.4v. Then take the multimeter/test light and flip the plug to the positive on the battery and check termainl #1 in that plug for ground. That is the main ground. Make sure you have a good ground where the light lights up, or it shows again the 12.4V or whatever. I would also check the ground on #18 on this plug, the signal ground. A good power and grounds to the TCM is a good start. The others you need a little better tool to test. But the power/grounds are a good place to start.

I suspect there is an issue with that plug/wiring to the TCM. It seems very common on these cars.

 

BTW if the indicators on the shifter do not show which gear, and it shifts hard into reverse that is 100% the TCM loosing connection. I doubt a TCM itself would only work intermittently. They seem to either work or fail. So again I would go back to wiring/ground/plug to that TCM.

You can even post a pic of your connector if you want. We are looking for loose pins, corrosion, and burnt spots. Or just ATF fluid. They get soaked a lot.

I would definitely start with the TCM first and then see what happens to the other codes once you get the TCM issue fixed.

 

Thank you for the response and sorry for the late reply, my work schedule is weird.

I cleaned the 7 grounds I could see on the passenger side (3 by radiator support, 2 under/near the battery, and 2 near the drive side strut tower) but I can't seem to get the TCM connector off, I see the gray lever goes to the side however it won't budge, is there something locking it in?

 

More than likely it's a worn/pinched wire. Either at the tcm harness near the plug or at Either front wheel abs harness

 

I had the same U0101 happen on my 2014 Impala (3.6L with the electronic 6T70E transmission.) I checked the battery and fuses and did some reading of the voltages and checked the ECM plug for damage or corrosion (but not the Tranny end due to weather and needing to get under the vehicle on a ramp or jacked up). Started a thread on here about it that discussed and showed some You Tube videos on the diagnostics and possible areas that could be involved.

Same symptoms from the standpoint of in limp mode, no lights on the console shifter to tell which gear it is in (other than visual of the number next to the letter) and when engaging the car in gear there was a clunk noise. If you are lucky it is a wire or connector issue that is causing it.

I ended up taking it to a local transmission shop to due further diagnostics and they in fact said it needed a new (remanufactured) TCM transmission module. The TCM unit you get either has to be programmed for the VIN on your vehicle by the company or taken to a dealer or shop that can do the update and programming. Since the TCM is in the transmission, they also recommended that the Transmission Valve Body be replaced at the same time. So I did both those items and it was been running for about 6 months now without further errors or issues.

 

I agree sounds like wiring or the pin connectors. Try cleaning the one you wiggle and even remove it from the connector harness and see if it is bent or damaged in anyway. In addition to the Ebay, probably can get the pins from either Digikey or Mouser Electronics also if that is closer or easier for you.