1996 Mitsubishi Montero Computer Reset

I recently had a sensor replaced on my 1996 Mitsubishi Montero. When I went to go smog it, I was told it would not pass because the computer had not reset itself and was advised to drive it for about 60 miles, which I did. 500+ miles later, the computer still has not reset - I am told it has completed some of the test, but not all. Any idea on how I can get it to complete the cycle of tests?