Can I add “not” after “but”.

[compiler]

The correct sentence is It is vehicle 2 fault but vehicle 1 is not.

Can I also say, “It is vehicle 2 fault but not vehicle 1” or “It is vehicle 2 fault but vehicle 1?”

Can I add “not” after “but”? Thank you for your answer.

 

[Tdol]

None of those sentences are correct. You could say:
It is vehicle 2's fault not vehicle 1's.
It is not vehicle 1's fault, but vehicle 2's.

 

[Matthew Wai]

How about 'Vehicle 2 but not vehicle 1 is at fault'?

Not a teacher.

 

[compiler]

How about It is vehicle 2 at fault but vehicle 1 is not?

 

[MikeNewYork]

Or "The fault lies with vehicle 2, not vehicle 1.