the terminator - Did the T-850 self terminate?

In Terminator 2: Judgement Day, the T-800 tells Sarah that he "cannot self terminate". I had always assumed that this applied to all Terminators.

But as Jason Baker points out in his answer to this question, it actually appears that the T-850 in Terminator 3: Rise of the Machines does something that could be considered self termination, albeit in an attempt (ultimately successful) to kill the T-X.

But one might argue that the T-850's "death" was less a matter of self termination, and more of a sign that Terminators are perfectly willing to allow themselves to be destroyed if it helps them complete their mission. For instance, the T-800 is actually the one who suggests that he should be melted down, because his mission was apparently twofold: 1. Protect John Connor (and obey his orders). 2. Prevent Skynet from coming online. The latter objective is the one that compelled him to let Sarah destroy him.

And in the first movie, the T-800 is so obsessed with killing Sarah that it ignores the hydraulic press it is crawling through to reach her. Again, this suggests that Terminators will disregard their own safety in order to complete their missions.

But the T-850's "death" is still slightly different from either of these other examples. The first T-800 didn't actively kill itself, it merely put itself in a situation in which it could be killed, because it was trying to complete its mission. And the second T-800 had already completed its mission, but was unable to self terminate, and needed Sarah to do the dirty work, so to speak. In neither of these cases did the Terminators kill themselves; rather, they both allowed themselves to be killed (in the first case, willingly, and in the second case, unwillingly).

The T-850, on the other hand, did actively kill itself. Granted, it killed itself in order to kill the T-X, thereby completing its mission, but it is hard to deny that its actions amounted to self termination.

So, as I have already said, we might assume that Terminators are capable of self termination if it allows them to complete their missions, and this might be all the explanation necessary.

However, there is another possibility: shortly before the T-850 self terminates, it is corrupted by the T-X and reprogrammed to kill John. It is seconds away from killing him, when John reminds him of his mission: to protect John Connor. This causes a sort of paradox, and the T-850 manages to shut itself down, thereby protecting John, and later overrides the new programming and reboots itself. This suggests that this Terminator has some degree of willpower, despite his statement to the contrary:

Desire is irrelevant. I am a machine.

We know that the T-850 is an upgraded version of the T-800, although the exact nature of the upgrade is not clear. It seems at least possible that the upgrades allowed this model of Terminator to self terminate.

Are either of these explanations correct, or is there some other option that I am missing? Did the T-850 self terminate, and if so, how was it able to do so?

Answer

This is specifically addressed in the film's official novelisation. In short, between the lowering door and the damage he'd suffered, the T-850's chances of remaining 'alive' were at zero percent. At that point, he was free to commit self-termination if it meant furthering his primary mission goal, keeping John and Kate safe:

I've edited for brevity and clarity.

The door was pinning their torsos even more tightly now. Nevertheless the T-X managed to bring the saw up from Terminator's chest, into his neck, and then into his chin and cranial case.

Still he did not release his grip, although with what little RAM was left in his cognitive circuits he finally reduced his chances of success to zero percent.

His body, broader at the shoulders and in the chest than the T-X's, was being crushed by the lowering blast door.

He could feel all of his systems going off-line, one by one. And there was nothing he could do to stop his own destruction.

One final course of action was left open to him. The only logical choice.

He released his grip on the T-X, and for a second their optical sensors locked together.

Terminator pulled aside the armor plating in his chest to expose his last hydrogen fuel cell. Without hesitation he yanked the cell out of his chest, trailing wires and mechanical parts, sparks and fluids flying in all directions.

She turned and fixed him with a baleful gaze.

"You are terminated," he told her.

Terminator crushed the fuel cell to rupture it, and thrust it into the T-X's mouth, driving it deep into her throat

"Eat me," Terminator said, and the fuel cell erupted with a tremendous explosion.