O2 Sensor Problem Again

here:

Do a google for -> mechanical 02 simulator

Your cat doesn't really enter into this, Dave. 141 is a trouble code regarding the heater circuit only. As far as output voltage, what you've described is normal. A warm engine running around 2-3k will produce a wave of .1 - .9v cycling 8-10 times per second. But anyway, what do you have on the heater circuit? This is where your problem lies. When you used that aftermarket sensor did you modify the factory harness in any way?

Try swapping sensors. The sensor after the converter basically monitors the performance of it. Did you check the condition of the front sensor? It needs to be clean with no powdery build up. The way you describe the millivolt reading, you may have a bad connection to the sensor itself, so it sets the code repeatedly. Just a thought.

No, nothing special. I just wasn't clear if you messed with the vehicle harness when you had that aftermarket sensor the first time...

Bosch OEM... that is an oxymoron.

Thanks everyone for all of the responses and here's my answer to each of your questions/comments:

Ph@boy said "Try swapping sensors": I can't swap the sensors, because the connectors are different, but I did the same test that I described previously on the pre-cat sensor and it checked out just fine.

High Tech Misfit said "Bosch OEM... that is an oxymoron": I realize that it's a semi-misuse of the term, but I was just trying to refer to the fact that it's not a "universal" O2 Sensor that requires splicing the connector.

Jeff Strickland said "Your trouble is NOT the output of the sensor, it's the sensor's 'pre-heater'": So does that mean that the O2 Sensor that I got is defective? Basically, what do I need to do to fix the problem?

Also, on a side note, the Haynes manual says that the code P0141 is set when the O2 Sensor reaches 600 degrees (or has run at least 2 minutes) and is not outputting 0.7 Volts.

Every> snipped-for-privacy@gmail.com wrote:

I understand what you're saying. But Bosch parts, universal or quasi-OEM, typically do not work well in Toyotas. I'm not sure who makes real OEM O2 sensors for Toyotas, NipponDenso perhaps?

I think the catalytic converter is not working properly and you have a problem with the O2 sensor heater circuit.

Me thinks you are correct. The original was most likely not bad either, however.

When a microprocessor is forced to operate outside of it design limits, by a problem as simple as a bad sparkplug, over time the sensor can become fouled. The result can lead to a bad sensor code, while to real problem is not discovered. As in your case the sensor will fail again shortly.

I would suggest you take the vehicle to a competent tech with the proper equipment to determine what is causing the microprocessor to operate outside of it design limits, and have it corrected

mike

The way to check catalytic converter function is with an exhaust gas analyzer. The technician takes an exhaust sample before the converter through the O2 sensor mounting hole and then takes another sample at the tailpipe. What comes out the tailpipe should be cleaner than what passes through the #1 O2 sensor mounting hole. Take the car to a competent technician for diagnosis and repair. I recommend using an OEM catalytic converter replacement if one is needed, and check to see if it is still covered by the emissions warranty.