Fig.1) The signal waveforms of front HO2S(the upper) and heater(the lower) at idle (chassis ground used)

Fig.2) The signal waveforms of front HO2S(the upper) and heater(the lower) at idle (sensor ground used)

Fig.3) The signal waveforms of rear HO2S(the upper) and heater(the lower) at idle (chassis ground used)

Fig.4) The signal waveforms of rear HO2S(the upper) and heater(the lower) at idle (sensor ground used)

Fig.5) The Normal data of HO2S heaters at idle (approx. 0.5A)

Fig.6) The data of HO2S heaters at open condition in HO2S(B2S1) circuit (0A)

The output voltage of front HO2S changes continuously according to air/fuel ratio. The PCM controls fuel amount based on this value. Preheating is necessary for HO2S normal operation. A heater unit is installed in each HO2S. The PCM can control air/fuel ratio with the output signal of HO2S simultaneous with engine run by reducing preheating time. The HO2S power source is the engine control relay. PCM operates heater by ground control.