I have a older 2006 Toyota Sienna van with close to 150K that had it's trans rebuilt 11k ago that has a 2-3 flare or slide bump but  no transmission codes. I replaced fluid and filter and SL1 and SL2 solenoids and installed a zip kit in the existing valve body, that did not resolve the issue. I went and obtained a used valve body and transfered the 2 new solenoids to the used valve body and that did not correct the issue. I then scoped out the transmission NC and NT speed sensors with my Maxi scope incorrectly and thought the NC sensor wasn't putting out the same amplitude I was seeing from the other, and got 2 good Transmission speed sensors from the same Donor transmission the valve body came from and got the same results from my scope until I scoped both the AC wave generating sensors from both sides of the speed sensors .

 The transmission guy said the ECM  could be the cause of the shifting issues and I bought a 2 day TIS sub to reflash the ECM but found out The present ECM calibration didn't show any newer level that I could reflash it to, and there was no option to Reflash the ECM over again to the same calibration level , so I wasted close to $50 just to find that it had no later level to reflash it.

 I have couple customer's with 2006 Sienna's that do not have a transmission shift issue mine has , but figured if I could plug my ECM into other car to try without having to reprogram all the immobilizer keys over even if a VIN mismatch code or ABS VSC lamp might come on , it would save me unnesssarily removing and going through the trans if I can Eliminate the ECM as the cause of the shifting issue.

  Has anyone swapped used 2006 Toyota ECM  and was able to start and drive temporarily for testing purposes with a VIN mismatch and not have to reprogram an immobilizer key in order to do so?

 I just want to try the ECM from the other Sienna for a short period to see if the same 2-3 shift flare occurs or not and then reinstall it back in the original vehicle without any programming of my vehicle's immobilizer, VIN mileage etc. to it.

  If van  doesn't start , the most I would attempt is get a non Immobilizer key blank cut that will turn my key cylinder and try to hold the other van's Immobilizer key head to the non immobilizer key to see if the key chip can  to be read from that vehicle's immobilizer key, so the ECM recognizes a familiar key and will allow van to start despite any VIN mismatch etc.