Grand Vitara 2WD V6-2.7L (2006)
Oxygen Sensor: Description and Operation
A/F Sensor Description
A/F sensor (1), in place of the conventional heated Oxygen sensor-1, is installed in the exhaust manifold (bank 1 and bank 2) and it consists of a zirconia
element (2) which causes the output current to vary according to difference in the oxygen concentration, a heater (3) which activates
the element and an adjusting resistor (4) which adjusts individual difference of the sensor.
A/F sensor detects oxygen concentration in exhaust gas (9) (A/F ratio of the air-fuel mixture) linearly, ranging from LEAN to RICH.
Operation
ECM (5) controls the sensor heater (3) and keeps the sensor element temperature at the specified level (about 750 degrees C) constantly so that the A/F
sensor is activated in the specified way for accurate A/F detection. When the sensor element reaches the specified temperature (it is activated), its
impedance drops to the specified value (approx. 30 Ohms) by its characteristic. When a certain voltage (about 0.4 V) is applied between sensor elements
in this state, circuit current corresponding to the sensor element impedance flows in the sensor circuit. ECM detects this circuit current and judges
whether the sensor is in the active state or not. At this time, sensor current is output linearly in the range of +0.01 mA to +some mA on the lean side and
- 0.01 mA to - some mA on the rich side. The variation in these ranges depends on the difference from the stoichiometry A/F ratio, that is, the amount of
oxygen between the atmosphere side (6) and exhaust manifold (7).
According to this sensor output, ECM executes A/F feedback (fuel trim) to achieve the target A/F ratio.
The A/F sensor connector (8) is provided with an adjusting resistor (4) ECM detects the adjusting resistance value and corrects the sensor output current
value.
