P0430 Chevy Express '97

billr

wrench
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Make
Chevy
Model
Express van, 1500 series
Year
1997
Miles
169K
Engine
5.7 V-8 w/4L60E trans
Any clues how to pin this down? Right now my only plan is to drive around and see how the O2 sensors are reading, maybe even swap them bank-to-bank. Fuel trims all seem reasonable (in the 1-4% range?) I can post info from a freeze-frame if anybody wants to play with me here...
 

grcauto

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Has it ran well for the 180K? It don't take much for a bad running engine to ruin the cat. Basically when the computer wants to test the cat when the conditions are right and the car is cruising it will change the fuel mix and looks to see that the REAR O2 sensor is much less active than the front. I have the factory info for that vehicle if you need any.
 

billr

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It has run (and still does) great for the whole time/miles. That is my plan, look to see what the O2 sensors are doing, but if the rear one is "lazy", I would like to determine if that is because of a bad cat or bad sensor/wiring. Therefore, the thought of swapping sensors from bank-to-bank. After 24 years they may not be so easy to get out, though...
 

Mobile Dan

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The "lazy" one you would be looking for would be an upstream sensor, I think. Typically, the pcm sets the code if up and down sensors are "too similar". And I doubt that downstream sensor would ever become too active.
 

billr

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I'll keep that in mind. Frankly, I am clueless here, looking for a definitive way to tell if the problem is a sensor reading (and which one!) or the cat. Maybe I should look at how the upstream sensor is responding to STFT? I know the upstream one should toggle back-and-forth past 450mV, at about a 1 Hz rate, and the downstream should mimic it at a much slower rate if the cat is working right.
 

grcauto

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Down stream sensor will be about .7 or so and move very slightly if the cat is functioning correctly. If the rear sensor is switching like the front sensor the cat is not doing it's job. You should graph a good minute or two of warmed up and cruising and see if the rear starts switching.
 

Mobile Dan

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If the engine runs good, and you have 2 upstream o2 sensors, you can just warm it up to closed loop and compare "wideness of sweepage". A bad one will hover around .500v and a good one will cycle across a wider range, maybe .200v to .800v. Should never reach .000v or 1.000v. If you have A/F ratio sensors the expected range is different. Centerpoint may be 2.500V with a total range of 0V to 5V. Better verify that with another opinion...
 

nickb2

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Maybe I should look at how the upstream sensor is responding to STFT? I know the upstream one should toggle back-and-forth past 450mV, at about a 1 Hz rate, and the downstream should mimic it at a much slower rate if the cat is working right.
Bingo, you just answered your own question

Here is a video I think you might find useful.

I do not VERY often endorse ppl or products, but this guy is very smart.

;)

Much more than me.

I think

 

nickb2

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At least he took the time to post a whole bunch of very useful stuff out there. I think I like him, and his info is on par with what I have learned and now know.

This one is older. Different guy, I remember scanner danner up here in montreal also.



 
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billr

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Yep, my first chore every time I login is to "sweep out the trash" (spam). Like NickD used to say, mostly a janitor now. were you ever able to find out about NickD?

I won't have anything new about the van until next week. My "test driver" (P) is out of town right now and I can't drive and pay proper attention to the live-data at the same time...
 

Mobile Dan

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If you can get it into closed loop in your driveway and watch STFT, you will probably get enough information to make a judgement.
 

billr

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Ha, I didn't think of that. Or maybe I am just to cheap to run it only for diag, not get some use at the same time!
 

nickb2

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using mode 6 should give valuable info also, so even if he isnt attentive, you should be able to see the integrators in mode six at time of coding. Integrators are short, block learn is long.

As usual, probably spell things wrong, so here is a download of something I caught in the internet a while ago, and I think it applies to gen 3 v8 which I think this van is. Or maybe a gen 2, honestly, I dont care what gen it is, the value of info is still the same.

I hope you read it bill, it thought this article was very well written, I liked the comparison charts from percentage to numeric, as not all car or scan tools give same values, so having a comparison chart is golden in those cases. After a while, you kind of get used to it.

Anyway, I will post that here, it is a pdf format, should not be a problem to read.
 

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