UPDATE
Bank 2 Sensor 1 wiring:
Red/Yellow (heater power, Pin 69) → Good.
Red/Blue (heater control, Pin 29) → Good.
Yellow/Blue (signal return/ground, Pin 70) → Good.
Gray/Red (signal, Pin 10) → Came back as open with no continuity. So I tested with all 70 pins at the pcm connector and still...