Problems begin when my brand new, out of the box Mechman 240amp alternator sent close to 20+ volts through my system due to a bad regulator and the switch to OS 12216125. I have dropped the trans pan and ohms checked the harness, TC solenoid, temp sensor, and replaced the Trans Fluid Pressure Switch. I'm also getting codes P1637 (Generator L- terminal fault) and P1810 (Trans Fluid Pressure Switch). I can hear the 1-2 and 2-3 solenoid click when commanded through the VCM controls but I can not get the TCC to lock using the controls while sitting still or driving. Oddly, if I put the shift selector in D3 while driving the PCM commands the TC to lock even though the tune is setup to not lock in 3rd. I have all cells in the Apply/Release Speed table maxed out except 4th up to 50%. When it locks in 3rd if stays locked but in 4th it will lock and unlock repeatedly when it reach the lockup speed. After all my checks I've found zero issues with the Trans (unless I missed something) so I'm now leaning towards the PCM. Thoughts anyone.

 

Did you ever figure this out ? I'm having the exact same issue