I can't speak to whether or not the bike will work without the TCD being connected, but I know for a fact it won't work if it still has the BLOKS display. The BLOKS display unit is easily removable and that, coupled with its small size, makes it easy to lose or misplace, and that may be what happened with this bike. If it is a BLOKS bike then it will not turn on without the BLOKS display unit attached. I also do not know when Specialized made the change from the BLOKS display to the TCD display, so it is likely that some 2019s came from Specialized with the TCD, but many 2019s definitely came with the BLOKS display, including mine, which has a very early build date.