I cleaned all ground terminals in the engine bay today. I also cleaned the alternator + post and properly re-did my battery post connections so they are tight and firm.
Battery read 12.6V, after starting the car, reads 13.5 / 13.6V... good sign... (lets hope it last...)
I also did some tests again with the TCM. I went on the road and monitored the Shift solenoid A and B terminals with a multimeter. As expected, they come On and OFF depending on the gear you select. They seam to work fine. I tested the TPS and switch again, all is within specs. This kind of point out to either a mechanical tranny problem, or the TCM that might still be fried or unprogrammed....
Again, what makes me believe that there's a "software" issue with the car is that the transmission drop back from 2nd to first gear whitout notice or being needed... Also, let's say I'm doing 75km/h and I punch the gaz, it'll try to engage 1rst gear even if the car is traveling way too fast... that makes me believe that the TCM has an improper "speed" refference somehow... I already swapped the rev sensor, I tested it also with a multimetter so I know it's alive. My abs and speedo works properly... I just don't know where to look now... There should be a "vehicule speed sensor" on the trasmission, just not 100% sure where to look...SOme say on top of the differential... I tested it's terminal on the TCM while on the road but it gave me all sorts of voltages... Don't know if they're good or not...
Can the ECM be unprogramed or fried and sending wrong data to the TCM ?
Is it possible to flash (reprogram) a TCM ??