Oxygen Sensors

Oxygen Sensors

Oxygen Sensor is a feedback sensor that tells ECU if there is oxygen in exhaust gas, so ECU can adjust the mixture close to Lambda 1 (14.7:1). Oxygen Sensor is passive sensor which does not require power to run, it outputs its own voltage. Purpose of the sensor is to protect the CAT.
Ledded fuel will destroy O2 Sensor as well as some silicone gasket makers.
In time O2 sensors become "lazy" they become less responsive and don't switch voltage as fast as needed. It's recommended to change them every 60 000 km or whenever engine light comes on.

O2 is similar 1V Battery. depending on amount of oxygen in exhaust gas it outputs a range of voltages from 0V to 1V. So the leaner the mixture the closer to 0V:


0V is lean
0.45V is ideal
0.9V is rich



Bosch O2 sensor wires colour code:
1 wire: Signal (black)
2 wire: signal (black) and earth(grey)
3 wire: heater wires (white) and signal (black)
4 wire: heater wires (white), signal (black) and earth (grey)

3 types:
Zicronia
Titania
Wideband

upstream and downstream (before and after CAT)

most new cars have 2 Before and after CaT to see if CaT working

V engines got O2 sensor per bank, so most of V12 got 4 O2 sensors

need to be at 500-600 degrees to operate properly


Wideband:

1 cell: 4 wires
2 cell: 5-7 Wires

tells how rich the mix is