I'm getting the above codes. In addition, while driving, every several minutes, the tach will drop to 0 for a second. I tried cleaning the batt terminals with the same results. I'm thinking maybe I need to pull the battery harness and clean/check all of the connections. Am I going in the right direction?

 

Sounds like you're on the right track - battery or grounds.
There's an important ground for the ECU, mounted between the ECU cover and the shock tower.