Diagnose the Oxygen Sensor
Introduction Learning Tasks Learning Assessment


Labscope waveform for an Oxygen Sensor

Diagnose the Oxygen sensor with a lab scope

With a little knowledge and a labscope, you can use the oxygen sensor signal to see how an engine is running.   With practice you will learn how well the oxygen sensor is working, find a fuel mixture that is too rich or lean, and see if the engine is misfiring.   After any engine service or repair you can use the labscope to quickly verify proper engine performance.

With this learning task you will explain how to use a labscope to test an oxygen sensor, and verify proper engine performance.

Oxygen Sensors are also commonly referred to as EGO (Exhaust Gas Oxygen) sensors, Lambda sensors, 02 Sensors, or Lambda Probes.   There are a few different basic types of sensors.   The most common type is the Narrow Band Zirconia Oxygen Sensor.  A very few vehicles will use Titania oxygen sensors and the newest style is the Wide Band Zirconia Oxygen Sensor.

For this learning task you should select any vehicle that uses a narrow band zirconia oxygen sensor.   Modern vehicles use a pre-catalyst and post-catalyst oxygen sensor.  You should focus your diagnosis and testing on the pre-catalyst oxygen sensor as this has the most influence over fuel control and will identify misfires and other engine performance malfunctions.