Mazda Protecta 2000 Automatic Box Problems

Help me please ... I have a Mazda protects 2000 with ZM engine, the box is failing, it changes alone to 3rd and that speed is stuck and makes it impossible to climb slopes, so that the box normally will work again, the car must be turned off but shortly after walking, again he only passes to third and is not able to climb slopes. The strange thing is that it does not send the box error code, can anyone help me?