One problem related to automatic transmission control module has been reported for the 2007 Toyota Prius. The most recently reported issues are listed below.
Cause: flat tire in the front left or front right of the vehicle. The front left demonstrating the most severe hazard failure: the traction control system engages regularly due to a discrepancy between the spare and normal tire size. Traction control cuts power to the drive wheels and cannot be overridden, causing vehicle to lose speed in non-deterministic manner. Vehicle is not responsive. Condition is worst during the first 40 miles driven on the spare tire but consequently improves due to learning inside the car computer. Unfortunately, vehicle is most dangerous when the driver has the least control over the situation. Correction: none, the manufacturer claims the vehicle is operating as designed.