Going through the code line by line won't help. The problem is the software was not programed to and unable to handle all possible real world scenarios. They likely never predicted the failures in their software simulations and IV&V.Statistics.... with 2 crashes within a few months, the rest of the historical data is of no use. Now, 737 Max may fly again next year. Engineers probably going through the code line by line.
The sin Boeing committed was after the first failure, instead of owed up they tried to explain it away.