It sounds like the TCM is going out or the input shaft speed sensor is not working correctly. For this problem you can get a CAN scanner from Amazon for about $30.00 here is a video to show you how. This can tell more of what's going on than a regular code reader.
Here is a scanner link:
Here are the instructions on how to replace the TCM and input shaft speed sensor in case this is what comes up in the diagrams below. Also, I have included the transmission wiring diagrams so you can see how the system works. Also, because the TCM is mounted with the electrical connector pointing upwards I have seen water get into the connector causing corrosion which can cause all kinds of issues. Remove the connector to check.
Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.
Images (Click to enlarge)
Friday, July 15th, 2022 AT 6:03 PM