Heated Oxygen Sensors (Ho2S)
Front heated oxygen sensor (HO2S)
The wiring to the heated oxygen sensors (HO2S) must not be squeezed or in any other way damaged. It is also not allowed to grease the contacts for the heated oxygen sensors as the oil in the fat would interfere with the reference air and the function of the heated oxygen sensors. Also areas where the cables attach to the body of the sensor must for the same reason be protected from contamination.
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 before the three-way catalytic converter (TWC). This is so that the engine control module (ECM) can continually check the combustion so that λ=1 is achieved. λ=1 is the ideal fuel-air ratio for the functioning of the catalytic converter which is 14.7 kg air per 1 kg fuel.
The heated oxygen sensor uses current control 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 sensors are an oxygen-sensitive ceramic body consisting of zirconium oxide among other things. 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 air lines or areas where the cabling attaches to the sensor body.
There is a front heated oxygen sensor.
The heated oxygen sensor can be diagnosed by the engine control module (ECM), and signals can be read out. For further information, see: DIAGNOSTIC FUNCTIONS
The control module can be used to read off the calculated lambda value from the heated oxygen sensor (HO2S) signal.
Rear heated oxygen sensor (HO2S)
The wiring to the heated oxygen sensors (HO2S) must not be squeezed or in any other way damaged. It is also not allowed to grease the contacts for the heated oxygen sensors as the oil in the fat would interfere with the reference air and the function of the heated oxygen sensors. Also areas where the cables attach to the body of the sensor must for the same reason be protected from contamination.
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 behind 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. Rear heated oxygen sensor (HO2S) has a fine-adjusting and barely measurable effect on regulation of the fuel/air mixture. The Engine Control Module (ECM) uses the signal to optimize the signal from the front heated oxygen sensor (HO2S).
For further information, see: DIAGNOSTIC FUNCTIONS
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).
There is a rear heated oxygen sensor.
The heated oxygen sensor can be diagnosed by the engine control module (ECM), and signals can be read out.
Preheating of the heated oxygen sensors (HO2S)
The heated oxygen sensor (HO2S) only functions above a certain temperature, approximately 300°C for the rear sond and 700°C for the front sond. The normal operating temperature is between 300-900°C and 700-900°C respectively. The heated oxygen sensors (HO2S) are electrically pre-heated so that operating temperature is rapidly reached. They are also pre-heated to ensure that the heated oxygen sensors (HO2S) maintain a normal operating temperature and to prevent condensation which could damage the heated oxygen sensor (HO2S).
The sensor's heating coil consists of a PTC-resistor. The heating coil is supplied with voltage from the system relay and is grounded internally in the Engine control module (ECM).
In order to avoid condensation damage to the heated oxygen sensor, current is initially pulsated from the engine control module (ECM). Depending on temperature, regard is given to the temperature in the dew and as the temperature in the PTC resistor increases, the resistance in the resistor increases, the current is reduced and gradually transferred to a non-pulsated current
The heating period for the front heated oxygen sensor is short, approx. 5-20 seconds (depending on application)
The heater element heats the heated oxygen sensors (HO2S) to approximately 350°C or 700°C respectively. The probes maintain this as a minimum temperature.
The engine control module (ECM) can diagnose the heater element.