I got code 12, how do I fix this?

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Just finished rebuilding my 1992, 2.2 toyota camry engine. It was a headache just gething the cams to be in sinc. I finaly got the hole thing done and most of my sensors are new. But I started the car And it was runing great. But the next day, it wouldnt start. I put the scaner to it and it gave me trouble code 12(Engine revolution signal missing). I changed the distributor and it started, but it shut down in the next minute or so. Is it a faulty distributor or the knok sensor just went bad. I need help fast, because this is the secon distributor I got for it and it doesent seem to be the issue. I made sure all conections and grounds are connected. Could someone please help?