Sidekick Sport 2D JLX 4WD L4-1.8L (1998)
Oxygen Sensor: Description and Operation
Oxygen Sensor Operation
It is necessary to keep the air/fuel mixture close to the theoretical air/fuel ratio (14.7) to obtain efficient performance of the three way catalytic
converter and high clarification rate of CO, HC and NOx in the exhaust gas. For that purpose, ECM operates as follows. It first compares the
signal from the heated oxygen sensor-1 with a specified reference voltage and if the signal is higher, it detects that the air/fuel ratio is richer than
the theoretical air/fuel ratio and reduces fuel. On the other hand, if the signal is lower, it detects that the air/fuel ratio is leaner and increases fuel.
By repeating these operations, it adjusts the air/fuel ratio closer to the theoretical air/fuel ratio.
1) When oxygen concentration in the exhaust gas is low, that is, when the air/fuel ratio is smaller than the theoretical air/fuel ratio (fuel is richer),
electromotive force of the oxygen sensor-1 increases and a rich signal is sent to ECM.
2) Upon receipt of the rich signal, ECM decreases the amount of fuel injection, which causes oxygen concentration in the exhaust gas to increases
and the electromotive force of the oxygen sensor 1 to decrease. Then a lean signal is sent to ECM.
3) As ECM increases the amount of fuel injection according to the lean signal, oxygen concentration in the exhaust gas decreases and the
situation is back to above 1).
