Oxygen sensors are a source of diagnostic information and often an overlooked service component. This article will address the zirconia oxygen sensor, which generates a voltage level up to 1 volt.
There are three basic performance aspects that a good O2 sensor should display.
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Figure 1 shows a good oxygen sensor waveform switching continuously above and below 450mV. The number of times the signal crosses the 450mV threshold is called cross counts. The cross counts will vary between one every two seconds to five per second depending on the type of fuel delivery system. Test the O2 sensor by running the engine at approximately 2500 RPM and press the F3 key to stop and save the recording to a file or select play current temporary recording. Select a recorded screen and press the F2 utility function and select the cursor function, Figure 2, and press the enter key. From the next selection box select Volt Difference.
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After selecting Voltage Difference the cursor will be displayed on the screen Figure 4 and require you to select the first voltage reference to be measured. Move the cursor left or right to the highest voltage level and press the ENTER key. Next, move the cursor to the lowest voltage level to choose the second point Figure 5 and then press the ENTER key. The two vertical dotted lines in Figure 6 mark the voltage at point one and point two and display the voltage at the top of the screen. Point one is 0.86V and point two is 0.08V and the difference D = 0.78V.
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The snap throttle test is a quick way to test the response time of a zirconia oxygen sensor.
A good sensor should switch from between approximately 0.175V and 0.800V in less than 100 milliseconds. This test is not valid if the oxygen sensor is unable to switch from 0.175V to 0.800V.
