[ermax]

Originally Posted by ninjabutt

My local guy, was a master tech at the Toyota dealership for years said you can't go backwards in ECU updates, at least not with techstream unless there's a way to trick the ECU into thinking the older calid is the update.

He also said all the different calids have different communication protocols which may be why I'm throwing the code.

If that's all true, I probably won't buy another ECU to check and will likely instead swap out the cam gear, swap my old ECU back in, and then watch the ILVs to see if bank 1 starts to come back up into spec, clearing codes each time. Any other options or info are welcome

That may be true when flashing with "Techstream" but flashing with other tools you can flash any calid you want onto any ECU you want. You just need to make sure it's a calid that is compatible with your car.