O2 Sensor testing procedure 1995 4Runner

Aug 10, 2004 1 Replies
A

Chilton's manual states the following:



  1. Start engine and bring to normal operating temp, then run engine above

1200 rpm
  1. Backprobe w/ a high impedence averaging voltmeter between the oxygen sensor and battery ground.
  2. Verfiy that the O2 sensor voltage is stablized at the middle of the especified range.

There are more steps. My question is what is "backprobe" and exactly how do I do it? I know how to use a voltmeter (sorta) but I never heard the term "backprobe". Note: I noticed 4 wires going to/from the O2 sensor. Colors were white, blue and 2 black wires. Not sure if I use these to backprobe.



TIA Darin


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Q

back probing is how you check for voltage without unplugging a connector or while a system is operating. In this case, you want to measure voltage @ the O2, but it needs to be plugged in in order for you to test, right? What you do is go to the connector, and with your DVOM set on DC voltage, find a ground with your black probe and put your red lead inside the connector where the wire goes in from the back. If it is a waterproof connector you may very thin probing extensions that will fit through the connector's insulation. Good luck, post if you have any other questions.

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