WS6 OXYGEN SENSOR ON THE VEHICLE

Before starting the experiment we located the O2 sensor. It’s placed in the exhaust pipe before the catalytic converter. It is three wires device, where two white wires are heater and ground and black wire is O2 sensor signal wire.

This is Zirconia switching type sensor. When the back probe was inserted we got this oscilloscope reading:

From this pattern you can see that voltage goes as high as 0.785 V and as low as 0.05 V. Unfortunately, our oscilloscope could not calculate an average voltage, so that we put on the paper approximate value of 0.4 V. The signal has 8 cross counts.

The signal is not uniform but fluctuates. For the normal condition I’d suspected misfire. However, in our case, it happens due to usage of aftermarkets ECU modules and program. The way how the O2 sensor is wired also plays role. Therefore, the oxysensor itself is working. This is a next in turn example that it would be wrong to say instantly that the device is faulty. The way of thinking must allow you to analyse the whole circuit and find out the real cause. This time this is how the O2 sensor is wired.

Consequences of this sort of wiring can be seen from the next test. The O2 sensor was heated up and RPM came down. It is expected to watch the pattern with cycling signal. But the signal we captured is not a good one:

The highest voltage is 0.016 V, the lowest voltage is 0.01 V. An average voltage is approximately around 0.011 V. We could not register the cross counts. The reason why it is so is described above.

Sudden acceleration brought us much better result:

 

The highest voltage was registered at 0.818V. This sort of O2 sensor sensing underlined that it reacts faster than 100 ms and sends the signal to the ECU that mixture is rich at the moment.

Once we accelerated and then dropped the pedal all the sudden we got this pattern:

The signal trend is normal, time of O2 sensor reaction is within the specification. But once again, bad wiring to the ECU module evoked fluctuations of the signal.

Instant acceleration in order to catch the pattern and count the time of O2 reaction is shot on this image:

Even though it is hard to count in our case, it is clear that from lean to reach sensor switches faster than 100 ms and to switch backwards takes a bit longer.

On the basis of all these tests and the information that O2 sensor is not wired proper way I tend to conclude the Oxygen Sensor is in operation condition. The more accurate conclusion can be made after testing this device or wiring it properly.