I got this code on the way home on Tuesday. First time, and I did some checking with my Superchips tuner on the way home. O2 sensor readings were all normal, so not sure why the code was tripped. Perhaps a blip.

Will be watching to see if it comes back.

disallow wrote:I got this code on the way home on Tuesday. First time, and I did some checking with my Superchips tuner on the way home. O2 sensor readings were all normal, so not sure why the code was tripped. Perhaps a blip.

Will be watching to see if it comes back.

Interesting...this is about a 2001 but I wonder if the same could apply with an R51?
http://autorepair.about.com/library/a/1i/bl775i.htm

Did the ECM recall apply to yours and if so did you have it replaced? I'm going to get mine replaced soon and see if that helps.
I wonder if some unscrupulous dealers are doing unneeded cat replacements and at the same time popping in a new ECM knowing that's the only problem?

Took a highway trip yesterday. I've been getting the odd P0430 code popping up over the past month or so. I think I figured it out. See the video below:

http://youtu.be/OX-V8rIE5nM

This was done while cruising at 110kph. Note how much the voltage reading jumps around on Bank 2 Sensor 2. Many times it actually goes below the voltage of Bank 2 Sensor 1. Pretty sure this is the logic the ECM uses to trigger a fault code.

So I will probably put the B2S2 sensor on my list of things to do this summer on the truck, and see where we end up!

Thoughts?

Will your Superchips allow you to record and view or export the voltage readings over a time period?

According to what I've read, the voltages should vary quite a bit over a few milliseconds and cruising or a constant RPM may not be a good indicator of O2 function.

Article on how to diagnose O2 sensor problems:
http://www.aa1car.com/library/o2sensor.htm

A good O2 sensor should produce an oscillating waveform at idle that makes voltage transitions from near minimum (0.1 v) to near maximum (0.9v). Making the fuel mixture artificially rich by feeding propane into the intake manifold should cause the sensor to respond almost immediately (within 100 milliseconds) and go to maximum (0.9v) output. Creating a lean mixture by opening a vacuum line should cause the sensor output to drop to its minimum (0.1v) value. If the sensor does not flip-flop back and forth quickly enough, it may indicate a need for replacement.

Also according to the article, an O2 sensor needs to respond quickly enough with a voltage jump during a throttle snap.

I tried some of the tips in this article on how to diagnose bad cats:
http://answers.yahoo.com/question/index ... 830AAzOPz0

My primary cats both show the 100 degree difference between front and rear leading me to believe one or more of my O2 sensors are bad but there are specific codes for bad O2 sensors which I'm not seeing leading me to believe I have a bad cat. He does state in the article that O2 sensors can function just well enough not to trip O2 sensor codes but does that mean they could be barely functional enough not to trip specific O2 codes but cause poor cat function and trip the broader P0420/P0430 codes?

It's a very tricky thing to diagnose O2 sensors if you don't know what you're doing. I wouldn't even know where to begin to hook up an oscilloscope like recommended in the article above.

I bought an OBD II code reader/diagnosis tool to record readings from my O2 sensors and this is what I saw. I was parked and snapped the throttle up to about 3k~4k RPM and back down to idle repeatedly for about 30 seconds to a minute and this is the readings of my O2 sensors.










If I'm reading this correctly, Sensor 1 bank 1 (drivers front O2) and Sensor 2 bank 1 (drivers rear O2) have bad readings.

To add to my confusion I believe if the ECM senses that the motor is running too rich in the case of a bad cat, the ECM will lean out the air/fuel ratio which would also adjust the readings of the O2 sensors. That seems to me to make it even harder to tell whether an O2 sensor or cat is bad when the O2 sensors could be self-adjusting for a bad cat.

According to the article, an O2 sensor needs to respond quickly enough with a voltage jump during a throttle snap. Based on that, the data I collected would lead me to believe sensor 1, bank 2 could be bad since it doesn't show a voltage change from zero for a much longer time than the rest.

Furthermore, my vehicle gets the same MPG it has always gotten and doesn't run poorly or idle roughly. I probably won't be able to help anymore as I've sold my Pathfinder. Good riddance Nissan!

Wow seems like Nissan has really strict specs on thier emission systems. Seems like the emissions warranty should be longer if they are going to do that, or lower the prices of the emissions parts.

The logic for setting the P0420/P0430 codes is the ratio between the upstream and downstream O2 sensors on a given bank. While driving, the ECM likes to see a 2:1 ratio (referring to the rich/lean cycling frequencies of the respective O2 sensors) between the upstream and downstream O2 sensors. If the ratio is at or close to 1:1, the catalyst media is inefficient and not breaking down the exhaust gases as it is supposed to do.

Seriously. That's all I did. Three weeks of regular unleaded and the code disappeared. It's been 4 days now.

Anyone else experience this?

I had the codes pulled with the possibilities of what it could be and they are: large vacuum leak(noone talked about that), fuel system fault, Ignition system fault(noone talked about that), and then the imfamous failed bank 2 catalytic converter. Has there been anyone that has checked these other areas and found success??

Yea you're correct.

But, the P0430/0420 are one of the if not the most difficult to diagnose because they cover a large array of possibilities. But the most common is the failed cat.


http://thenissanpath.com/viewtopic.php?t=2305

Check the last link and DL the FSM. It has all the info you need/seek.

I know this is an old thread, but I need some advice. I have the P0430 code, but I do not think it is my cat. My reasoning is based on my O2 sensor readings. If I am correct, sensor 1 is before the first cat and sensor 2 is after. With the car engine off or at idle, sensors 1 and 2 on bank 1 both read 0.3 V. On bank 2, sensor 2 also reads 0.3 V, but sensor 1 reads 0.6 V. Similarly, as I drive the vehicle, sensor 1 on bank 2 always reads much higher than all the other sensors (and it is the only sensor that exceeds a reading of 1V). The post cat sensors on both banks always have similar numbers. Am I correct to assume my pre-cat sensor is faulty?

Hi Guys,

Anyone know where I can find a tutorial on how to install 02 spacers? I have the same SES code P0430.

Thanks!

You Tube:

This one if for a Mini Cooper, but the process is the same. This one shows a CEL Eliminator:

https://www.youtube.com/watch?v=EuEsevIXE7Q

This vid shows how to make an oxygen sensor spacer out of a spark plug anti-fouler:

https://www.youtube.com/watch?v=GqDmmLQ4pGk

smj999smj wrote:You Tube:

This one if for a Mini Cooper, but the process is the same. This one shows a CEL Eliminator:

https://www.youtube.com/watch?v=EuEsevIXE7Q

This vid shows how to make an oxygen sensor spacer out of a spark plug anti-fouler:

https://www.youtube.com/watch?v=GqDmmLQ4pGk

Thanks SMJ. But do you have any pictures of where exactly I can find the sensor? If it's P0430 then it must be at the driver side correct? I just want to know where exactly.

Thank you!

Trust me when I say you'll be able to find the oxygen sensor under your car. Crawl under and and follow your exhaust coming out of either piston bank. You'll see a wire and plug heading into two places down the length of either exhaust pipe. The first one will be infront of the first cat and the the second will be after the last cat for both pipes. The catalytic converters being the bulges in the pipe.

Sorry if I got too basic in the explanation about the cats. I dont know what level of experience you have with this stuff.