A simple oxygen sensor question revisted, for the first time

Everyone knows that a zirconia oxygen sensor produces its own output voltage (0.1 to 0.9 volt), right?

The four-wire planar zirconia oxygen sensor has two wires for its heater (12 volts power and a neutral wire). Its oxygen sensing element has an output wire, and a input wire carrying 5 volts.

The why: why does the oxygen sensing element, which generates a voltage, need an external 5 volts?

Simple question, right? Simple answer?

It’s a wideband oxygen sensor. Read about it here:

if the o2 sensor has 5 volts then it is a wideband 02 sensor also know as a air fuel sensor…

A wideband zirconia oxygen sensor seems to fit; but, in an econo. 1998 Ford Taurus (3.0L DOHC)? Parts descriptions, at different online sites don’t mention “wideband” …just “planar”. How does one know?

uhhh! training.maybe?

wideband funny though.

It looks to me that wideband sensor is current driven rather than voltage driven. The regulated 5 volts supply would seem to be the tip off about the type of sensor. Here is what the info stated about it:

“An electronic circuit containing a feedback loop controls the gas pump current to keep the output of the electrochemical cell constant, so that the pump current directly indicates the oxygen content of the exhaust gas. This sensor eliminates the lean-rich cycling inherent in narrow-band sensors, allowing the control unit to adjust the fuel delivery and ignition timing of the engine much more rapidly. In the automotive industry this sensor is also called a UEGO (for Universal Exhaust Gas Oxygen) sensor.”

From the information I’ve gathered, the 1996-1999 Ford Taurus uses a planar, narrow-band, zirconia oxygen sensor. Wideband O2 sensors have FIVE wires, not four.
The online sources say that a bias voltage may be applied to O2 sensors; but, on the Ford, is there a bias voltage? On the Ford charts (alldata), the circuit (PCM 91) looks to be a common power supple (5 volts) for ALL the sensors; but, it’s labeled as, “SIGNAL RETURN”. Would a signal return carry supply voltage?! PCM 60, for B1S1 O2 sensing element, is labeled as, “HO2S Input” to the PCM.
Is PCM 91 the signal return path for ALL the sensors? That doesn’t seem right.