02 Sensor

[corollave]

I have 2000 corolla i recently had the engine check light come on. I put it on the code reader and the code that came up was a p0171 system to lean bank 1. I narrowed it down to the to the oxygen sensor, so i removed it from the car to bench test it and noticed that it was white in color. I did some research and found out that if the sensor is white in color i have been using some sort of silicone that is not sensor safe and basically will poison the sensor and make it no good. One other thing that was said in the article was i could have a head gasket leak, there are no leaks! I can't think of anything i would be using that is silicone base that would cause the sensor to turn white like this. Just wondering what the problem could be. Thanks

[DaiFai]

You probably need a updated Mass Air Flow Meter from Toyota; it should throw a different code if your O2 is no good.

[corollave]

when you say "mass airflow meter" you mean sensor right?

[fishexpo101]

How did you determine that the sensor was bad? Did you backprobe the sensor and check out the resulting waveform on a scope? White color could be from coolant contamination or fuel contamination - but can also be a result of standard fuel additives. Don't go so much on the color, as if it was setting P0171 code a lot, you could have been running lean for some time - that will make the O2 sensor take on a shiny, white color too.

A common thing to check is the MAF. Your 2000 Corolla has a Mass Airflow Sensor (MAF) that is in the airbox, right above where your air filter is.

If that sensor gets dirty - if could cause a P0171 Lean code to be set. A quick fix is to try cleaning the sensor first - they make MAF sensor cleaner or you can use throttlebody cleaner / brake cleaner - just make sure that they are non-chlorinated, as it will eat the plastic.

[corollave]

I just cleaned the mass airflow sensor and I am still having it pull the same code. I bench test my o2 sensor by taking it out of the car and throwing some heat on it while looking to see if it could get to 9 tenths of volt on a volt meter and then seeing if the voltage would drop quickly. i got no voltage at all. I never did backprobe it though, not sure if that would make difference?

[fishexpo101]

Backprobe is useful if you are measuring the output in real-time. Otherwise, bench testing - you'll just touch the leads directly. This is a four wire sensor - made sure you hit the signal wires? Should be blue, white, and two black leads - blue and white are signal and ground, both black wires are for the heater.

What did you use for heat - a propane torch? Got to get it pretty hot.

[corollave]

yeah i used a propane torch and i had it on there for awhile, enough that it should have shown some sort of voltage. If i am to backprobe do i back probe right from the sensor itself and if so what kind of numbers am i looking for. Just a jump in voltage?