WS6 Oxygen SensorThere are 3 main types of Oxygen Switches
Zirconia switching
Titania switching
Air fuel Ratio
Zirconia type oxygen sensors switch between 0-1V with 0.45 as the Lambda value. When the engine is running lean, the voltage will be around 0.3V or less. When running rich, the voltage will be around 0.8V or more. This information gets sent to the ECU which adjusts the fuel trim depending on what the oxygen sensor is reading.
Titania type oxygen sensors switch from 0-5V (some are 0-1V) but unlike Zirconia type oxygen sensors, the resistance changes when reading the oxygen. 20K Ohms lean, and 1K rich.
Air Fuel Ratio type oxygen sensors not only tell the ECU that the engine is running lean or rich, it tells the ECU how much the engine is running lean or rich. This type of sensor uses 2 sensors that communicate with each other to determine how rich or lean the mixture is.
Locate an oxygen sensor on your vehicle. Describe where it's located.
Near the bottom RHS of the Exhaust.
How many wires for this oxygen sensor?
3: Black = signal out. White = Heater +. White = Heater -
What type of oxygen sensor is this?
This type of oxygen sensor is zirconia type.
With an oscilloscope connected to the Oxygen sensor signal wire, we recorded the Pattern with the car at 2500RPM.
As you can see from the graph, the voltage reached to about 1V, and the voltage was continuous. The average voltage as shown on this graph was 0.5V.
When we increased the RPM of the car, the oxygen sensor jumped up, and at cruise, the vehicle fluctuated from 0.4V to 0.6V
We then used an oscilloscope to measure the output voltage on the vehicle at idle speed
The voltage in the graph goes up to 0.5V, and maintains constant while the car is at idle. We counted no cross counts with this graph.
Our next task was to make the engine run rich and capture a pattern on the oscilloscope.
As you can see from the graph, the oxygen sensor went up to 0.85V. This is from the oxygen sensor detecting more fuel in the combustion chamber.
The next task was to make the oxygen sensor go lean by doing sudden deceleration from 3000rpm.
I included the Red Line on the graph from the theory notes, because although they may look different, the Blue line is "aliasing". The voltage goes as low as 0.038V when we decreased the throttle from 3000 rpm
Our next task was to measure the response time of the sensor. We measured the voltage as the oxygen sensor went from lean to rich.
This oxygen sensor is good because the signal wire is switching from 0-1V.
which is what a zirconia type oxygen sensor wire does. When we added propane to make the engine run rich, the voltage from the oxygen sensor went up. When we made the engine run lean, the oxygen sensor decreased in voltage. In conclusion the oxygen sensor that we tested on this vehicle is working to specifications and does not need replacing.
References: Google Images, Unitec Blackboard Oxygen Sensors PowerPoint
