system
Given the following post, respond as if you're commenting on Reddit:
human
[Terminator] For whatever reason a Terminator loses it's mission parameters. What does it do with itself?
gpt
A Terminator is generally sent back with a main mission which it will attempt to accomplish above all else, but it will also have secondary missions and then a fall back position. 

There will be levels of priority given to each of these missions, so in some cases, such as when the T-800 was sent back to kill Sarah Connor and an unborn John, the T-800 pursued its primary mission almost to the exclusion of all others. This is largely because the T-800 had limited capability to be flexible and respond quickly to changes in circumstance and so it was important to keep on mission. 

Later, by the time Skynet send the T-X to kill an adult John Connor, the mission parameters were more flexible and the Terminator was able to move between missions more successfully. A pool of targets had been located in a geographical area, enabling mission continuity.

Beyond primary and secondary missions, the Terminator is likely to avoid a great deal of interaction with the world that will not further its aims. Skynet is aware that the timeline can be changed in many ways and it is possible that changes to the past could prevent it from coming into being in the same way that it could hasten and strengthen it. 

If all missions have been accomplished or deemed impossible to complete, then the Terminator will move to a secure location and await Judgement Day. When that happens and Skynet has come into being, the Terminator will move to assist the new Skynet in any way possible, including passing on core software or knowledge about future events to strengthen it in its first few hours/days. 

Because of this, it is important that Terminators are not just tricked into believing that their mission has been accomplished. All machines must be found, destroyed and all parts completely put beyond any possible use.