I have the Hanes manual for the GSR P72, and it says that pin 6 is O2 sensor heater control (02HTC) on the wiring diagram... the wire for O2 signal is WHT/RED, but when I spliced voltmeter in for poor man's A/F gauge, it just reads like 1.0V +or- 0.3V... So I don't know, I got P28 chipped with GSR program, but o2 is the same on OBD-1... It's supposed to read from 0.1V to 0.9V for lean and rich mixture respectively.
Later,
Mike