"cause" vs "caused" [closed]

The first one would be correct.
"An unexpected condition caused an error".

You could use the other form however that one would be to say that it will or it is causing the error. It might be worded like this but probably wouldn't fit.

"An unexpected condition is the cause of the error".

To me, the first one sounds better.

On a computer the error normally occurs first and the the error message comes later, so "An unexpected condition caused an error". If the error is ongoing the message might be "An unexpected condition is causing an error". This would be less common because the response to an unforeseen error is more likely to be a system halt.