Signal Wave Form & Data

This figures show the wave form measured at terminal 2 of HO2S at idle RPM.

Fig 1: Signal WAVE FORM - Terminal 2 Of HO2S At Idle RPM

Courtesy of HYUNDAI MOTOR CO.

1. The average voltage of HO2S should be 0.5 V.
2. When sudden deceleration, the voltage at point (1) should be below 0.2V.
3. The switching time marked (2) from lean to rich should be within 200ms, if longer than 200ms HO2S may be not good.
4. The switching time marked (3) from rich to lean should be within 300ms, if longer than 300ms HO2S may be not good.
5. In case the average voltage of HO2S is over 0.6V.

   Possible cause: Injector leakage, faulty Pressure regulator Faulty MAPS, ECTS.

6. The rear oxygen sensor output is usually not changeable like front oxygen sensor, however, if it moves like front oxygen sensor, the catalytic converter is broken.

   If you release the accelerator pedal suddenly after engine running about 4000 RPM, fuel supply will stop for short period and the O2 sensor service data in the Hi-Scan (Pro) will display values 200mV or lower. When you suddenly press on the accelerator pedal down, the voltage will reach 0.6~1.0V. When you let the engine idle again, the voltage will fluctuate between 200 mV or lower and 0.6~1.0V. In this case, the O2 sensor can be determined as good.