O2 sensor test

[lk1ng04]

Is there a full proof way to test the o2 sensor?

[S12_Lifer]

Worth the money to buy new.  You know how strict smog can be in Cali.............unless you know someone.

[Wonderingraven]

Check FSM, but easiest way for me is, does it change the way it operates when you unplug the o2 sensor? the ECU relays heavily on that o2 sensor, i think disconnected it would run extremely rich if I recall.