Heated Oxygen Sensor (HO2S): Troubleshooting: Waveform

Fig 1: HO2S Signal Waveform (1 Of 2)

Courtesy of HYUNDAI MOTOR CO.

Fig 2: HO2S Signal Waveform (2 Of 2)

Courtesy of HYUNDAI MOTOR CO.

Fig1) The signal waveforms of front HO2S(the upper) and heater(the lower) at idle

Fig2) The signal waveforms of rear HO2S(the upper) and heater(the lower) at idle

The HO2S requires a minimum temperature to provide a closed loop fuel control system. So the HO2S contains a heater element to reduce its warm-up time and ensure its performance during all driving conditions. The PCM controls this heater element by duty cycle. The main relay supplies voltage to the heater and the PCM provides a ground circuit for activating the heater.