Civic L4-1668cc 1.7L SOHC MFI (2003)
Oxygen Sensor: Description and Operation
Primary Oxygen Sensor
Primary Heated Oxygen Sensor (Primary HO2S) (D17A1, D17A2 engines)
The primary HO2S detects the oxygen content in the exhaust gas and sends signals to the ECM/PCM which varies the duration of fuel injection
accordingly. To stabilize its output, the sensor has an internal heater. The primary HO2S is installed in the three way catalytic converter (TWC) (D17A1
engine) or in the exhaust manifold (D17A2 engine). By controlling the air fuel ratio with primary HO2S and secondary HO2S, the deterioration of the
primary HO2S can be evaluated by its feedback period. When the feedback period exceeds a certain value during stable driving conditions, the sensor is
considered deteriorated and the ECM/PCM sets a DTC.
