How to Test Resistance of O2 Sensor Heater

In this video I'll show you how to test the resistance of an O2 sensor heater using a digital volt/ ohm meter. The O2 sensor featured in this video is a 3 wire O2 sensor. However, the information is applicable for testing 4 wire O2 sensors also. The process is very simple. First, you have to identify the two wires going to the heater of the O2 sensor. Once these wires are identified by color you'll need to find out what pins the wires go to on the harness side of the O2 sensor connector. Then you disconnect the O2 sensor connector and prob the pins on the component side of the connector that the pins of the two heater circuit wires connect to. Take your resistance reading and compare it to the specification in your manual.

The O2 sensor heater is the component inside the oxygen sensor responsible for heating the sensor up more quickly than the exhaust would. Engineers found that by adding a heater to an oxygen sensor the sensor heats up more quickly. Of course the sensor only operates correctly at a very high temperature. So, the more quickly the sensor is heated up the more quickly the sensor can be used to accurately monitor the exhaust gas. This helps in getting the vehicle into "closed loop" more quickly and improves fuel economy and emissions.

Note: When probing pins inside connectors use care not to damage pins. Placing probes that are too large into connectors could spread female pins and cause a poor pin fitment condition. If probing a female pin be sure the probe is the same sized as the male pin that connects to the female pin. This will insure you don't cause damage to the pin.

Also, not every wire schematic will look like the one shown in the video. You'll need to read and understand your manual and wire schematic for the vehicle you are working on in order to identify the correct wires to prob.

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Repair your vehicle at your own risk! Barbour's auto help does not guaranty a proper diagnosis using these techniques.