'00 and'01 are the years for the bad diode, but I don't know the build dates yet.
Usuallly when they quit working, you have no 2nd at all. They usually explode.
Sounds like you may have a sticking 1-2 shift valve. Service your trans "change fluid and filter" and add either Lucas or Lubeguard. DO NOT use any other brans of trans additive. These 2 can be found at O'reilly or Auto Zone. Preston