Rear heated oxygen sensor (HO2S)
The rear heated oxygen sensor (HO2S) is used to provide the Engine Control Module (ECM) with information about the remaining oxygen content of the exhaust gases beyond the three-way catalytic converter (TWC). This information is used by the Engine Control Module (ECM) to check the function of the three-way catalytic converter (TWC). This check is carried out when the conditions for the catalytic converter diagnostics have been met. The rear heated oxygen sensor (HO2S) has no direct effect on regulation of the fuel/air mixture. However the Engine Control Module (ECM) uses the signal to optimize the signal from the front heated oxygen sensor (HO2S). For further information, see:
For S60/ S80/ V70/ V70XC/ XC70: Three-way catalytic converter (TWC) diagnostics .
For XC90: Catalytic converter diagnostic .
The heated oxygen sensor (HO2S) uses voltage control. The signal characteristic is binary. With a binary signal characteristic, the amplitude of the signal curve changes considerably when changing the oxygen content in the exhaust gases. Otherwise its components and function are the same as the front heated oxygen sensor (HO2S).
The wiring for the heated oxygen sensors (HO2S) must not be trapped or damaged in any way. The connectors for the heated oxygen sensors (HO2S) must not be greased under any circumstances. The oil in the grease would disrupt the reference air and the function of the heated oxygen sensors (HO2S).
The engine control module (ECM) can diagnose the rear heated oxygen sensor. The signal can be read using VIDA.