Trouble codes 12 and 65 - '97 3.5

The other day my MIL came on as I was cruising down the highway. There was no hesitation, noise, etc. I checked the codes using the key method and got 12 (problem w/ battery connection) and 65 (short or open condition in MTV circuit).

I have had a horrible time keeping corrosion off my positive battery cable & post and I clean it up a couple times a year, and last year put on a new one b/c there was almost nothing left of it. So I'm thinking this is what's causing the poor connection at the battery. The corrosion has creeped down the cable between the copper strands so I'm thinking the only way to fix this is replace the whole cable...would this be right?

Onto the MTV circuit...anyone out there had this code/problem? I'm wondering if the usual plan of action would be to test the wiring and try to trace it to a short, or if replacing the valve would solve the problem. Any insight would be greatly appreciated.

Thanks!