washer only agitates during heavy duty cycle

My Kenmore washer won't agitate on reg or perm press cycle but will on heavy duty . Could it be the timer or the drive motor?

Hello,
It sounds like one of the speeds are out in the motor.
It is possible that the low speed is out. Sometimes this happens for the spin cycles too, may only spin either on high or low spin, but not both.
Sounds like a motor to me.
If you have anymore questions please ask. I will be more than happy to help you further.
Bill