holmesnmanny

The manual says to test for continuity between terminals A and B. I tested using the lowest setting which is 200 and got 4.0. It says if resistance is not 14-40 replace sensor. Is it safe to assume that this sensor is bad or is that reading 40 instead of 4.0 ? I had just bought this sensor but when my first engine was put in and had the bad 4th cylinder that was leaking coolant i'm wondering if it got fouled up.

thanks in advance

PT-Tuner.com

I thought part of the procedure to test the oxygen sensor is to heat it up, aka take a torch to it.

GhostAccord

If I'm not mistaken he is performing the test for the O2 heater circuit.


Holmesnmanny,
If you are testing the heater circuit and you are only getting 4.0Ω with your meter set at 200Ω. Then your O2 heater circuit resistance is out of spec.

Setting your meter to 200 is not a multiplier. 200 is the range that the meter will measure up to. ex, it will cover from 0-200Ω If you need to measure something that is over 200Ω you will need to set the meter to the next setting. Usually 2kΩ (2000Ω / diode test mode)

clempot911

+1 on what GhostAccord said.

There are 2 tests you can do - the heater and the actual O2 sensor element. Sounds like you are doing the heater. Just make sure you have the right pins. If you were testing the sensor itself you can do it using a propane torch, heat the tip with the blue 'cone' on the torch and read the voltage out the 2 pins (NOT RESISTANCE). IIRC it should be over .500mv with the torch on it, then drop to 0mv with no torch.

holmesnmanny

ya that was the first test it gave. I didn't have to go any further because I failed that one. lol


luckily I still had it under autozone warranty by two days lol

ya it was pretty clear on which pins

thanks

phootbag

At no time in my career have I had to heat an oxygen sensor with a torch to test its operation.

GhostAccord

I agree, Generally most people would just leave the sensor in the car and start it up. When the car is at operating temps the O2 sensor output should read 0.1v or less. As long as there are no fuel supply issues that is.

holmesnmanny

lol ya, sounds a wee bit dangerous for my taste. Mine was charcoaled up a bit. Not too sure why it would be that way after only a few months driving it but I think the first engine having a coolant in the combustion chamber leak and now me seeing that my map sensor is bad had to have affected it.

clempot911

It’s just a way to bench test them – you can do the same on the car, forcing it rich/lean, but this is good if you have one on a salvage engine or a used one you saved and want to know if it’s good or not. If the heater element is bad it doesn’t matter anyway, he needs a replacement.

These guys did a video on how it works.
http://www.youtube.com/watch?v=stFhLSHsOGg


If the fuel system is working right and the O2 sensor reads 0.1v or less you have a dead sensor. It should be swinging above and below 0.5v if everything is working. The switching is fast, some cheap meters can't show it.

GhostAccord

Oh yeah sorry bout that, got my figures mixed up, you are correct. It should be approx. 0.6v @ WOT to 4500rpm then quickly sweep below 0.4v when the throttle is closed.

JamesB1985

Yes, and the best way to test the Oxygen Sensor (not heater element) is with an Oscilloscope. You're able to view the switching rates (cross counts) of the sensor. The sensor is also checked for its rich-lean and lean-rich switch times.

There was a guy who wrote an article recently in 'MOTOR' magazine about it. He said to make sure you heat up the engine properly, then do a test at 2000 RPM. ...here's a little bit from the article.. He was testing a Civic:

"I described one type of oxygen sensor check
in the August column; I’ll suggest another one
momentarily. To recap that first test, hold the
throttle at a steady 2000 rpm and scope the O2
sensor. Usually, a good sensor shows three traits
during this test: First, the signal repeatedly and
consistently cycles rich/lean. Second, it makes at
least seven or eight rich/lean cycles within 5 seconds.
Third, the signal ranges from about .10
volt up to .90 volt. The scope pattern on page 12
of the August issue shows a prime example of a
good oxygen sensor signal."

Some tech's will not let the sensor heat up to the proper temp and they will not make the best diagnosis or be able to see a lazy, or bad Oxygen sensor.
You can also do a snap-throttle test to check for a "lazy" O2 sensor.

exb18c1

I will say that this test is pretty good for the dead sensors but absolutely not accurate for checking the real time operation.When you are suspecting a bad oxygen sensor you always have to make sure that the circuits are in good condition otherwise you are starting from the back.And some sensors are not really want to come out that easy in home environment.Plus the code that will trigger the owner to suspect the sensor already directs you toward the problem.For the person who does't have any idea about operation and acting of an oxygen sensor it wouldn't help much.The sensor itself is the last piece in the chain to check.When you reach to that point it means that you have checked the rest excluding the ECM right?But before changing an ECM I wouldn't rely on the propane torch test!Your opinions?

JamesB1985

My opinion is yes the Propane test just seems silly to me. Just like the other guy said, in all his years working, he never used it. If you exhaust all your other diagnostics and haven't figured it out, maybe try it as a last resort but that's all.
Maybe if bored sometimes i'll try it.

holmesnmanny

It didn't say, but should I have tested it for resistance with the car on ? With the sensor heated up to operating temp ?

exb18c1

the resistance test is for the heating element and the temperature doesn't play any role here.You have to start with the description of the code anyways,it will split the tests. and by the way , never test resistance on the live component!