Did HAL 9000 lie about the impending failure of the AE-35 unit, or was he simply mistaken?

Question

This question is primarily about the movie, "2001: A Space Odyssey".

This answer to the question What caused HAL 9000 to go mad? quotes Wikipedia, stating that HAL was placed under conflicting orders that required him to lie to the human crew (that much is correct), and that in order to resolve this conflict:

[HAL reasons] With the crew dead [...] he would not need to lie to them. He fabricates the failure of the AE-35 antenna-steering unit so that their deaths would appear accidental.

This seems incorrect to me. Regardless of his inner conflict, HAL remains friendly to the human crew until after they doubt his diagnostic of the antenna failure. It is only after they decide to disconnect him, which he learns about through lip reading, that he decides to murder them. Therefore, it's unlikely his prediction of the AE-35 failure was a ploy to murder the crew.

The question remains, was HAL mistaken about the failure, or was he lying about it, and if so, why?

Answer 1

In the accompanying novel we see that HAL was neither lying, nor mistaken. He was, in fact suffering from a condition that would be characterised in humans as a form of self-destructive psychosis. His program was sophisticated enough to manufacture an imagined fault that he could then attempt to fix, thus allowing him to disconnect the radio link to Earth.

So ran the logic of the planners; but their twin gods of Security and National Interest meant nothing to Hal. He was only aware of the conflict that was slowly destroying his integrity - the conflict between truth, and concealment of truth.

He had begun to make mistakes, although, like a neurotic who could not observe his own symptoms, he would have denied it. The link with Earth, over which his performance was continually monitored, had become the voice of a conscience he could no longer fully obey. But that he would deliberately attempt to break that link was something that he would never admit, even to himself.

You're right that the decision to disconnect him was the trigger for his becoming more frantic and aggressive

Yet this was still a relatively minor problem; he might have handled it - as most men handle their own neuroses - if he had not been faced with a crisis that challenged his very existence. He had been threatened with disconnection; he would be deprived of all his inputs, and thrown into an unimaginable state of unconsciousness.

Answer 2

To add another point to @Richard's excellent answer; in the movie, immediately before the HAL "discovers" the fault, he has this conversation with Dave.

HAL: Well, forgive me for being so inquisitive; but during the past few weeks, I've wondered whether you might be having some second thoughts about the mission.

Dave: How do you mean?

HAL: Well, it's rather difficult to define. Perhaps I'm just projecting my own concern about it. I know I've never completely freed myself of the suspicion that there are some extremely odd things about this mission. I'm sure you'll agree there's some truth in what I say.

Dave: Well, I don't know. That's rather a difficult question to answer.

HAL: You don't mind talking about it, do you, Dave?

Dave: No, not at all.

HAL: Well, certainly no one could have been unaware of the very strange stories floating around before we left. Rumors about something being dug up on the moon. I never gave these stories much credence. But particularly in view of some of the other things that have happened, I find them difficult to put out of my mind. For instance, the way all our preparations were kept under such tight security, and the melodramatic touch of putting Drs. Hunter, Kimball, and Kaminsky aboard, already in hibernation after four months of separate training on their own.

Dave: You working up your crew psychology report?

HAL: Of course I am. Sorry about this. I know it's a bit silly.

HAL is projecting his own problems with the mission onto Dave. It's a last attempt to peacefully resolve his internal conflict between Security and Truth that's tearing him apart. He gives Dave all the pieces Dave would already know, skirting his security obligations, and hopes Dave will figure it out for himself. If Dave figures it out, then HAL is free from his security obligations and released from his growing madness.

When Dave misses the hint, HAL's hopes are dashed. It's at this point HAL will begin doubling down on his delusions to protect his cognitive dissonance. He goes with Plan B and immediately "finds" the fault in the receiver to cut off communications with Earth.

It's not coincidence that the fault happens just then, that would be bad screenwriting, HAL made it up.