It cranks but won't start. Did it with no warning and no check engine light....

What is your question?

I think i have an electrical issue with my 2000 Crown Victoria not turning over. Will crank but won't start. We narrowed it down the last few days to a power to ground that had a short coming from the engine wire harness. We cut the Red wire and the car started up. Its running rough with a bad miss. So, not sure if i need to replace the harness or if its an O2 sensor or not. My mechanic says it's Failed/shorted B2S1 O2 sensor. Would this stop the car from starting?