[Jeff Chambers]

O2 readings should be toggling. That's how the computer manages when in closed loop. Only in open loop will you see a steady O2 output, hopefully at your commanded lambda. In closed loop, the O2 should toggle anywhere from about .1V to .8V with .45V being stoichiometric. The computer will add a small amount of fuel; when the O2 responds with a voltage above .45V the computer then removes a small amount of fuel and looks for the O2 voltage to fall below .45V. This toggling action is the computer's management of fueling. It then learns and makes corrections based on the amount of fuel it has to add to induce this toggling.