Chapter 26 in 2010 "Probation"
I'm still wondering why it took so long for HAL to become schizophreniac.
Besides, these things were only explained in 1982 when ACC wrote 2010...
Ah, and another thing: if HAL indeed knew about TMA1 and had to hide it, why does he only reveal he could read their lips (when Dave wants to return aboard) and nothing about the real mission. HAL could have raised Dave's curiosity (and prevented the lobotomy) by revealing as much as possible before being disconnected.