Heated Oxygen Sensor 1 (HO2S 1)

Figure 1 Heated Oxygen Sensor 1 (HO2S1) Output:

Figure 2 Heated Oxygen Sensor 1 (HO2S1):

DESCRIPTION
The Heated Oxygen Sensor 1 (HO2S 1) is located on the right side of the exhaust manifold and detects the concentration of oxygen in the exhaust gases. It consists of the zirconia element (with thin platinum surface coating) which generates electromotive force, a lead wire which draws out the electromotive force, a heater which promotes activation of the zirconia element, lead wires for the heater power and ground circuit and cover and housing which protect the zirconia element from damage.

ZIRCONIA ELEMENT
The zirconia element, by its property, generates the electromotive force when a difference in oxygen concentration exists between its faces. As its temperature rises, the change of the electromotive force is amplified by catalytic reaction of the platinum. The HO2S makes use of this property. Atmosphere is introduced into the HO2S, the inside of the zirconia element is exposed to the atmosphere and outside to exhaust gases. Thus, the difference in concentration between the inside and the outside of the zirconia element varies with the oxygen concentration in the exhaust gases.

OUTPUTS
The large concentration difference results in about 1 volt of the electromotive force and a small difference results in about 0.01 volt. To put this in other words, if the amount of oxygen in the exhaust gases is less (air-fuel mixture is richer than the stoichiometric mixture), about 1 volt of electromotive force is generated and if more (air-fuel mixture is leaner than stoichiometric mixture), almost none is generated. In this way, the HO2S detects whether the oxygen concentration is high or low (the mixture is leaner or richer than the stoichiometric mixture).

Figure 2 Legend

1. Heater Circuit
2. Terminal Post
3. Element Cover
4. Heater
5. Zirconia Element