Recently started having transmission issues. When in D, trans shifts hard from gear 2 to gear 1, When in 3rd there are no shifting issues at all. Thought it might be a fluid pressure problem so I changed the fluid and filter, problem persists. Pulling OBD codes p0700, p0731, and p0846. I have been doing some research into having to reprogram or "reflash" the TCM to fix his issue. But before I take it to a shop to have that done, (I do not have access to the DRB 3 Scan tool) I wanted to see if there are any tests that I can do prior to taking into the shop to rule out the solenoid pack, and other sensors, like the transmission speed sensor, fluid pressure sensor. ect ( things I can do with the tools and equipment I have available to me). Any input you all have would be much appreciated.

 

I had this problem some time ago. I went to my local transmission shop. The Tech connected a gizmo that reported to him some code or other that he knew was wrong and he corrected it. The tire size had been incorrectly entered as well. Went for a test drive all was good. $25.00.

 

One thing that you can do which is quick and easy is take a look at the TCM connector, which is accessed by pulling the driver side splash panel in the front wheel well. These things have a history of getting corroded, so disconnecting and cleaning it is something worth trying. You should also check for a leaking solenoid pack, which is often the first sign of that part going South. That said, it sounds more like a pressure switch, based on the specific P0846 code. I wouldn't reflash the TCM, but if you wanted to try some easy part hanging and throw a few $$ at it, you could replace the TCM with a reman from one of the online computer parts outfits (around $200).