Front Oxygen Sensor
The wiring to the oxygen sensors must not be squeezed or in any other way damaged. It is also not allowed to grease the contacts for the oxygen sensors as the oil in the grease would interfere with the reference air and the function of the oxygen sensors. Even the area where the cable harness connects to the oxygen sensor body must be protected from contamination for the same reason.
The front oxygen sensor 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. 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 parts air per 1 part fuel (parts by mass).
The 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 oxygen sensor consists of a preheating element and the actual oxygen sensor.
Oxygen sensor
The oxygen sensor, which is part of the oxygen sensors, is an oxygen sensitive ceramic body consisting of zirconium oxide, among other things. The Engine Control Module (ECM) supplies power to the ceramic oxygen sensor, 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 oxygen sensor needs reference air from the surrounding air. This reference air reaches the oxygen sensor via its cabling or where the cabling connects to the oxygen sensor body.
Preheating element
The normal operating temperature is between 700-900 °C. It does not work below 700 °C. The oxygen sensors are electrically pre-heated so that operating temperature is rapidly reached. Heating also ensures that the oxygen sensors maintain a normal operating temperature and to prevent condensation which could damage the oxygen sensor.
The oxygen 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 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 oxygen sensor is short, approx. 5-20 seconds.
The oxygen sensor, including heating element, can be diagnosed by the Engine Control Module (ECM), and signals from the oxygen sensor can be read out.