2007 Supra 22SSV. Check trans warning comes up on computer screen when going more than ~18MPH. Warning goes away when slowing back down to ~5MPH.

Transmission and VDrive fluid levels fine. Seems to run fine otherwise, but haven't run it hard when warning comes on.

Mobile mechanic had computer error code reader and the code would just pop up as 'General Error'. Would reset code and then it would come up again next time got to ~18MPH.

Any ideas?