Contour Enthusiasts Group Archives Forums General Troubleshooting bench check of O2 sensor - possible or not?

Lots of replacement of these on Contiques.

Is there anyway to bench check proper operation of a sensor using a simple voltmeter/ohmeter and perhaps 12 volt battery power?

Alternately can you connect to wiring harness of car and check without installing sensor in manifold?

No. It must be installed and up to temperature. So that is no on both questions.

Thanks for reply.

A supplementary question: I thought they had a built-in heater which simulates operating temp until manifold heats up?

It is possible to bench check an O2 sensor if you have a propane torch (no acetylene welding torches, they will destroy the sensor...)

Hold on a sec while I do a google search...

Here are some sites that detail the procedure:

http://www.shotimes.com/SHO3badO2sensor.html

http://www.mr2.com/TEXT/O2_Sensor.html

Note that on the 4-wire O2 sensors, the multimeter should be measuring the voltage from the black/grey wires.

The instructions say to hold the O2 sensor in a vise-grips and connect the ground from the multimeter to that.

I am not sure but I do not believe that 4-wire sensors are grounded that way because the 4th black wire is there to provide a more reliable ground than through the exhaust manifold, so hook the ground from the multimeter to the black wire.

Also check across the two white wires for resistance of a few ohms--this is the heating element connection, sometimes the element opens up and doesn't heat anymore. This will appear as infinite resistance and is sufficient cause for replacement.

Brian

They do have a heater, as my previous post mentioned, but it's nowhere near powerful enough (by itself) to heat the O2 sensor element to the approx 600F it needs to be to operate.

It does speed up the warmup process, and prevents the O2 sensor from cooling too much at idle.

Brian

qaz:
Thanks for reply and the links.

Excellent information qaz. I'm always learning something from this group. Thank you.

using a simple voltmeter/ohmeter



It depends what you mean by "simple". If this is a digital, high impediance meter, then you are fine. An old analog meter will bleed the charge off of the O2 sensor and give you a false reading. It's like putting a low resistance short across the sensor.

A digital multimeter with a bargraph function would be the best for testing O2 sensors--the bargraph updates faster than the numeric display.

Brian