Anyone have a stock Civic VX and can measure the Oxygen Sensor voltage signal for me. My 1993 Civic VX shows a 0.78V on the White wire of the sensor with the key in the Ignition position. After starting the engine and letting it run for 1-minute the voltage goes to 2.8V. The factory service manual says it should be below 0.4V. I have replaced the ECU and 5-wire (wide-band) Oxygen Sensor but it still shows the same voltages. My car continues to failed smog (15mph Nox too high) because the EGR will not open. My guess is that it is stuck in open-loop mode.

 

the VX O2 sensor has two signal lines so those voltages sound about right.
Are you throwing a CEL?