Retrieving Transmission Codes

So for the last 3 days I have been finally driving the car to diagnose all the drivability issues I need to sort out, one of the reasons is the computer goes into limp mode. I was finally able to get it to go into limp mode today so now I need to know how to read off codes for the transmission which I am not seeing anything on how to do that. I also changed out the TCM today to see if anything changes and it was all the same.



So for the background behind it, before it goes into limp mode it shifts 1-3 just fine but does not go into 4th at all, then limp mode comes and it is only 3. I am driving around 50 mph.



Man this thing is fun before limp mode comes in.

Retrieving Transmission Codes