Kia 2004.5 Spectra Service Technical Training page 140

2004.5 Spectra Technology
This process is carried out by a miniature pump (pump
cell), which supplies the electrodes on the exhaust
side with enough oxygen to ensure that the voltage
between the electrodes remains a constant 450mV.
The PCM interprets the current consumption of the
pump cell to determine the air-fuel ratio value.
The Wide Range oxygen sensor expands on the
principle of the Nernst unit or "oxygen sensor" by
being coupled to a pump cell. And it's through this
small slot (gap) in the pump cell that the exhaust gas
enters the actual small diffusion-monitoring chamber.
In normal sensor operation, a small sample of the
exhaust gas passes through the diffusion gap into the
pump cell. This exhaust gas is rich or lean, which is
sensed by the reference cell, which produces a voltage
"Vs" above or below the PCM's voltage reference signal
(Vref).
A rich exhaust will produce a high "Vs" voltage and
the electronics produces a pump current "Ip" in one
direction to consume the free fuel. A lean exhaust
produces a low "Vs" and the electronics sends the
pump current in the opposite direction to consume
free oxygen.
Driveability
22