I don't show them as A and B with the service info that I have. It lists them as 1-2 and 2-3 shift solenoids. If I had to guess, 1-2 may also be referred to as A. If you are going on a fault code description, what is the code? P0751 and P0753 are faults that relate to 1-2 solenoid. This info is also under the assumption that we are dealing with a 4L60e transmission(1500 series). I will attach an illustration.