i have the ford 555C TLB... the shop/service manual is well worth the cost. tip a soda can on its side = thickness of book. goes over everything tearing it apart and putting it together along with full trouble shooting info. and specs and what to check. the shop/service manual i think was around 150 maybe 200 bucks, but well worth it. granted you need some mechanical knowledge of how to work on things, and some 12v d/c electrical knowledge (how to use multi meter) basic stuff. but most part it is all there.
for the unit i have, there are 3 buttons, on the shuttle shift lever left side of steering wheel, one button on the FEL joystick, and another button on the gear shift lever. any one of these buttons could be the issue.