When driving up a hill, undesired upshift to 4th gear is prevented from taking place when the accelerator is released. This minimizes the chance of subsequent downshifting to a lower gear when accelerating again. This prevents repeated upshifting and downshifting resulting in a smoother operation of the vehicle.

NOTE
The transmission may downshift to 2nd or 1st gear, depending on the way the accelerator pedal is pressed to accelerate the vehicle again.