How do you test oxygen sensors on cars?

Answer 1

With the engine running and sensor in place, connect leads to the ECM leads from the sensor. A digital voltmeter on 20 VDC will register the fluctuations in voltage (moving in a one-volt range). A sensor that generates a fluctuating voltage is generally good. Some sensors take a few minutes to warm-up.

See a repair manual on your car (such as Hayne's) for a more in-depth description.

Answer 2

Ren is basically correct however, a sensor that registers is not necessarily good. A truly good sensor is one that responds quickly. To test for fast response you must vary the rich/lean condition of the exhaust. This is easily accomplished by adding air/ fuel to the engine while running and test leads are connected.

I use compressed air added to the intake plenum to create a lean condition(to much may cause engine to stall/backfire). I use a small bottle of propane with a torch head and a hose clamped to it and connect it to the intake plenum to create a rich condition.

You want to add the air or propane in quick short bursts while idling the engine at 1500 to 2000 rpm and watching the voltmeter for quick (almost instant) responses remembering, the quicker the better. You can also rig this to test while driving. A slowly moving needle indicates a bad sensor. Soot in the tailpipe and backfires in the intake are also indicators of a bad O2 sensor.

On fuel injected cars replacing the O2 sensor is part of a good tune-up they should be replaced at regular intervals regardless.

If you want to buy an O2 sensor tester/test equipment Ebay has them for around $100 depending on the vehicle and are somewhat application specific, a general use shop tester costs $300 to $1000 for a handheld unit.

Answer 3

With a scan tool .Take it to a pro,let them daig it and pay them.
most of the time the o2 sensors is not the problem,just the messenger.