Transmission

Sudden problem. Appears to be in limp mode. Check engine light on, scan revealed the following - 31-2 pfinh signal malfunction, 61-1 battery voltage low, po706 transmission range sensor circut range /performance, p0740 torque converter clutch p0730 incorrect gear ratio, po706 transmission control system. Batter voltage is 12.7 volts per my meter, fluid level correct, but brown and dirty and slightly burnt smell. Fluid and external filter have been changed every year. Wondering If range sensor and fluid would account for codes, but hate to change them out till I get more advice. Runs, shifts fine up to 40 mph, and will rev high if you try to push it faster. Believe this is limp mode, not slipping but not sure. How would you proceed.