Skylark V6-3100 3.1L VIN M SFI (1996)
Oxygen Sensor: Description and Operation
Fuel Control Oxygen Sensors
Fuel Controlled Heated Oxygen Sensor (H02S 1)
The fuel control Heated Oxygen Sensor (HO2S 1) is mounted in the exhaust manifold where it can monitor the oxygen content of the exhaust gas
stream. The oxygen present in the exhaust gas reacts with the sensor to produce a voltage output. This voltage should constantly fluctuate from
approximately 100mV (high oxygen content - lean mixture) to 900mV (low oxygen content - rich mixture).
The heated oxygen sensor voltage can be monitored with a scan tool. By monitoring the voltage output of the oxygen sensor, the PCM calculates
what fuel mixture command to give to the injectors (lean mixture low HO2S voltage = rich command, rich mixture-high HO2S voltage = lean
command).
The HO2S 1 circuit, if open, should set a DTC P0134 and the scan tool will display a constant voltage between 400 - 500mV. A constant voltage
below 300mV in the sensor circuit (circuit grounded) should set DTC P0131, while a constant voltage above 800mV in the circuit should set DTC
P0132. A fault in the HO2S 1 heater circuit should cause DTC P0135 to set. The PCM can also detect HO2S response problems. If the response
time of an HO2S is determined to be too slow, the PCM will store a DTC that indicates degraded HO2S performance.
To control emissions of Hydrocarbons (HO), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), a three way catalytic converter is used. The
catalyst within the converter promotes a chemical reaction which oxidizes the HO and CO present in the exhaust gas, converting them into
harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The PCM has the ability to monitor this
process using the HO2S 1 and the HO2S 2 heated oxygen sensors.
The HO2S 1 sensor produces an output signal which indicates the amount of oxygen present in the exhaust gas entering the three-way catalytic
converter. The HO2S 2 sensor produces an output signal which indicates the oxygen storage capacity of the catalyst; this in turn indicates the
catalyst[prime ]s ability to convert exhaust gases efficiently. If the catalyst is operating efficiently, the HO2S 1 signal will be far more active than
that produced by the HO2S 2 sensor.
