Signal Wave Form & Data

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

Fig 1: WAVE FORM Measured At 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.

The amplitude of the signal output of the rear HO2S is small compared to the front HO2S because the rear HO2S detects emission gas purified by the catalytic converter. This is the normal signal WAVE FORM of the rear HO2S at idle.