Check Eng./ETS Lights on

'97 pontiac grand AM, 2.4 4cyl. Check Eng./ETS lights are on. When coded computer reads slow/low reading from O2 sensor 1 Bank1. After changing O2 sensor twice :banghead: still get the same reading. By using a multimeter the O2 sensor seams to be functioning properly with the exception of if the vehicle is in motion and the excelorator is let up on causeing a coast motion the O2 sensor read 0.0 Volts :banghead:Could this be caused by the Idle Air Control Valve? :eek7: