Long time reader, first time poster....

I have a 2010 Mazda 3 iSport with 96k miles. A couple of nights ago tried to reverse and it "clunked" into gear. AT light, traction light, and CEL come on. Never had this problem before, no hard shifting etc. When I started driving there was little power, stuck in a gear, prob 3rd. No lights for transmission position.

I read this is what is called the Mazda 3 "limp" mode and CEL code U0101 appears as "Lost communication with TCM".

Is this as simple as finding corrosion, bare wire, along the wiring to/from the TCM? Or is it for sure the TCM itself? Also, where is that TCM? Some posts say its on top of the transmission, others say under the batter box with the Turbine Speed Sensor.

I have never flushed transmission fluid, but would dirty fluid (it's really not that bad) cause this? Would a failed solenoid cause the TCM communication loss? Or is this all electrical only to or from the TCM?

Quite a bit of info out there, but not much direct resolution. If anyone could tell me exactly where the TCM is on this 2010 Mazda 3 or instructions/video to replace, that would help.

Thanks!