GE washer will not agitate but will rinse and spin

Machine will not agitate and will spin and rinse in only some settings. I have replaced the agitator coupler and have inspected the belt which looks good. I am thinking timer control next? I just hate to spend another $125 if I am not sure!

What does it do after it fills? Does it make any noise at all? If you move the timer knob side to side and up and down, will it do anything at all?

It will hum and act like it wants to kick on but will not actually move. When you move to a different setting the only one that works consitanlty is power rinse. On that setting washer spins and works correctly. If you just move the knob it will not change anything unless you go to power rinse.