XC90 2.5T AWD L5-2.5L Turbo VIN 59 B5254T2 (2003)
The front heated oxygen sensor (HO2S) is used to provide the Engine Control Module (ECM) with information about the remaining oxygen content of
the exhaust gases in front of the three-way catalytic converter (TWC). This is so that the Engine Control Module (ECM) can continually check the
combustion so that lambda=1. lambda=1 is the ideal fuel-air ratio, with 14.7 kg air/1 kg fuel.
The heated oxygen sensor uses current regulation and its signal characteristic is linear. With a linear signal characteristic, the amplitude of the signal
curve is low when changing the oxygen content in the exhaust gases. The probe consists of a preheating element (see "Pre-heating heated oxygen sensors
(HO2S)") and the actual lambda sensor. The lambda sensor is an oxygen sensitive ceramic body consisting of zirconium oxide. The control module
supplies power to the ceramic body, which reacts to the oxygen content of the exhaust gases. This in turn affects the signal to the engine control module
(ECM). In order to determine the oxygen content in the exhaust pipe, the heated oxygen sensor needs reference air from the surrounding air. This
reference air reaches the heated oxygen sensor via the wiring.
Caution! 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 heated oxygen sensor. For further information, see Heated oxygen sensor (HO2S) diagnostic See:
Powertrain Management/Computers and Control Systems/Description and Operation/Heated Oxygen Sensor (HO2S) Diagnostic. VIDA can be used to
read off the calculated lambda value from the heated oxygen sensor.
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 See: Powertrain Management/Computers and Control
Systems/Description and Operation/Heated Oxygen Sensor (HO2S) Diagnostic
For XC90: Catalytic converter diagnostic See: Powertrain Management/Computers and Control Systems/Description and Operation/Three-Way
Catalytic Converter (TWC) Diagnostics.
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).
Caution! 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
