Torque Pro Readings on O2 Sensors

[EatonKyleH]

Is there another test for the rear 02 sensor? I checked the resistance and that was fine, so now I am looking at the catalytic converter as a possible source of my P0420 unless you some other diagnostic pages. The only test Alldata gives me is the resistance test. Beyond that, I am still playing around with the Torque app to see my O2 sensor voltage when running.

Indeed there is.


1. Monitor the front and rear oxygen sensors while driving the vehicle at approximately 55 MPH. When the rear sensor switches above and below 0.45 volts, the catalytic converter may be faulty. The rear oxygen sensor should read about 0.6 to 0.7 volts when the catalytic converter is efficient.

2. Monitor the fuel trims both at idle an while driving at steady speeds. Fuel trims should be in single digit ranges and the short fuel trim should be increasing and decreasing 2 or 3 percent. When the fuel trims are out of range, there is a fuel mixture problem or a faulty oxygen sensor and this should be corrected before calling the catalytic converter faulty.

With California emissions you will disregard the front A/F sensor but the rear sensor voltage values and operation are the same as above.

 

[TheDurk]

Is there another test for the rear 02 sensor? I checked the resistance and that was fine, so now I am looking at the catalytic converter as a possible source of my P0420 unless you some other diagnostic pages. The only test Alldata gives me is the resistance test. Beyond that, I am still playing around with the Torque app to see my O2 sensor voltage when running.

To be honest, I wasn't smart enough to figure out a way to discriminate between a degraded rear O2 and a bad cat using my Torque Pro. (I have since seen EatonKyle post the same thing as he did here--I have it bookmarked--and I would definitely have tried that if I had possessed that wisdom at the time.) I had the same issue as you, the only difference was I had replaced my A/F eleven months previously due to a P1135 as opposed to getting the p0420 right away.

I considered that:

1. The rear O2 was as old as the faulty A/F and they often die at more or less the same time.

2. The cat showed no sign of physical damage or made any noise typical of a broken substrate, nor was there any sulfur smell.

3. Many people on here have resolved their P0420 by replacing an older rear O2. Mine was old enough that it was end-of-life even if it wasn't the problem.

4. A rear O2 is a pantload cheaper than a new cat and I would want one anyway if I put a new cat in.

So I rolled the dice and swapped it and two years later I have had two p0420, one that occurred when I was driving through a crowded state park on a Sunday with a strictly enforced 15mph speed limit for 45 minutes. This seems to upset the system, something about the cats not getting hot enough to work right. I reset and it never came back until....

It is worth doing a very minute inspection for exhaust leaks. The other P0420 occurred nine months ago and I found a very slight leak at the first flange after the front A/F sensor. New bolts and gasket fixed that. So don't dismiss the exhaust leak possibility without a thorough check. I had to get right up against the flange with a thin piece of paper to detect that leak. Our exhaust gaskets and bolts are at a suspect age.

Currently I am CEL free. To be honest again, if changing the o2 had not worked, I had been planning to go to the URD sim before I would swap cats. These Cali. systems are over-sensitive and it is not worth spending serious coin just to satisfy an over-picky ECU.)

Obviously, YMMV. Keep in mind that these Toyota cats are built like a brick sh!thouse and they rarely fail if there is no physical damage and engine is well-maintained so that it never runs rich (as in don't ignore CEL's for things like p1135, which I addressed quickly and I guess you did, too. If a P1135 is not addressed, the engine stays in open-loop, therefore runs rich, which is a cat death sentence, as excess fuel causes the guts to overheat and destroy itself.)

 

[IBallEngineer]

So I rolled the dice and swapped it and two years later I have had two p0420, one that occurred when I was driving through a crowded state park on a Sunday with a strictly enforced 15mph speed limit for 45 minutes. This seems to upset the system, something about the cats not getting hot enough to work right. I reset and it never came back until....



Currently I am CEL free. To be honest again, if changing the o2 had not worked, I had been planning to go to the URD sim before I would swap cats. These Cali. systems are over-sensitive and it is not worth spending serious coin just to satisfy an over-picky ECU.)

Obviously, YMMV. Keep in mind that these Toyota cats are built like a brick sh!thouse and they rarely fail if there is no physical damage and engine is well-maintained so that it never runs rich (as in don't ignore CEL's for things like p1135, which I addressed quickly and I guess you did, too. If a P1135 is not addressed, the engine stays in open-loop, therefore runs rich, which is a cat death sentence.)

I had P0420 one time for just a day, I scanned it because Torque free sucks. The next day the CEL went out and it hasn't been back. I'm curious if anyone has any experience using one of these, it's an O2 simulator.

~original[/IMG]

 

[shadow247]

To be honest, I wasn't smart enough to figure out a way to discriminate between a degraded rear O2 and a bad cat using my Torque Pro. (I have since seen EatonKyle post the same thing as he did here--I have it bookmarked--and I would definitely have tried that if I had possessed that wisdom at the time.) I had the same issue as you, the only difference was I had replaced my A/F eleven months previously due to a P1135 as opposed to getting the p0420 right away.

I considered that:

1. The rear O2 was as old as the faulty A/F and they often die at more or less the same time.

2. The cat showed no sign of physical damage or made any noise typical of a broken substrate, nor was there any sulfur smell.

3. Many people on here have resolved their P0420 by replacing an older rear O2. Mine was old enough that it was end-of-life even if it wasn't the problem.

4. A rear O2 is a pantload cheaper than a new cat and I would want one anyway if I put a new cat in.

So I rolled the dice and swapped it and two years later I have had two p0420, one that occurred when I was driving through a crowded state park on a Sunday with a strictly enforced 15mph speed limit for 45 minutes. This seems to upset the system, something about the cats not getting hot enough to work right. I reset and it never came back until....

It is worth doing a very minute inspection for exhaust leaks. The other P0420 occurred nine months ago and I found a very slight leak at the first flange after the front A/F sensor. New bolts and gasket fixed that. So don't dismiss the exhaust leak possibility without a thorough check. I had to get right up against the flange with a thin piece of paper to detect that leak. Our exhaust gaskets and bolts are at a suspect age.

Currently I am CEL free. To be honest again, if changing the o2 had not worked, I had been planning to go to the URD sim before I would swap cats. These Cali. systems are over-sensitive and it is not worth spending serious coin just to satisfy an over-picky ECU.)

Obviously, YMMV. Keep in mind that these Toyota cats are built like a brick sh!thouse and they rarely fail if there is no physical damage and engine is well-maintained so that it never runs rich (as in don't ignore CEL's for things like p1135, which I addressed quickly and I guess you did, too. If a P1135 is not addressed, the engine stays in open-loop, therefore runs rich, which is a cat death sentence, as excess fuel causes the guts to overheat and destroy itself.)

Well the check engine light has been on for a while, I have been getting consistent 20mpg on road trips, and 16 around town, so I figured it was no big deal. The only reason I am now trying to fix the light is to pass TX state inspection in 2 months. I am moving for a job next week, but I will technically be a VA resident for another month, giving me 2 to get the problem sorted.

I will try to check out my voltages and fuel trim as suggested and report back.