LAMBDA SENSORS.
TWO TYPES, ZIRCONIA AND TITANIA.
ZIRCONIA, The most common type which produces a voltage, a low voltage indicates a high oxygen content and a lean mixture, a high voltage indicates a low oxygen content and a rich mixture.
This information is sent to the electronic control unit which constantly adjusts the fuel accordingly, ECU.
IDENTIFICATION: Fistly identify the number of wires on the sensor there wil be a choice of either, one, two, three or four wires options, the wires could be coloured as follows.
One wire, Signal wire. Black.
Two wire, Signal wire. Black.
Earth wire. Grey or white.
Three wire, Signal wire. Black.
2 Heater. White.
Four wire. Signal wire Black
2 Heater White
1 Earth Grey.
The thread size is 18 m/m.
TITANIA, The ECU supplies the sensor with a ref voltage, the resistance is measured, when the exhaust gases contain excess oxygen (the engine is running lean) the resistance is high. When the exhaust gases has little or no oxygen( the engine is running rich) the resistance is low. Titaniun sensors fall into two catagories the first as three wires;
One Wire Heater Postive Red.
Second Wire Heater Ground White
Third Wire Signal Output Black
Could also have a fouth wire.
Fouth wire Refrence voltage Yellow
The thread size is 12 m/m.
Hope this helps