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P0420

  #11  
Old 03-10-2019, 08:16 AM
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I cannot help, my ride does not have the secondary air installation...
 
  #12  
Old 03-10-2019, 03:58 PM
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Originally Posted by FUN-V View Post
any ideas?
Not sure exactly what you are trying to fix. If it is a P0420, clear the code and see if it returns. If it is a pending P0420 then say so. The tests you posted don't make much sense to me - what is Test OC60? Screen capture that says not done looks like an emissions readiness test. If so, not done would mean the test was not run yet (not that it has a problem). To diagnose a P0420 compare plot of upstream o2 sensor voltage with that of the downstream O2 sensor at 2000 rpm in park. The downstream O2 sensor should not cycle rapidly like the upstream sensor if the catalytic converter is doing its job.
 

Last edited by LesMyer; 03-10-2019 at 04:05 PM.
  #13  
Old 03-10-2019, 08:05 PM
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was just trying to diagnose the p0420, to figure out if it really is the cat or something else.
Just pulled the whole walker cat assembly (WALKERŪ EXHAUST SYSTEMS :: E-Catalog Lookup) out of the warehouse and will replace it, even at cost $250 is a chunk of change i was trying to avoid.
 
  #14  
Old 03-10-2019, 08:28 PM
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Originally Posted by FUN-V View Post
was just trying to diagnose the p0420, to figure out if it really is the cat or something else.
Just pulled the whole walker cat assembly (WALKERŪ EXHAUST SYSTEMS :: E-Catalog Lookup) out of the warehouse and will replace it, even at cost $250 is a chunk of change i was trying to avoid.
I don't blame you at all. So do you want to diagnose the problem, or just go ahead and replace the cat converter?
 
  #15  
Old 03-10-2019, 11:12 PM
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Well I already bought the cats, but haven't installed them yet.
I don't know how to interpret the data from the scanner, so that would be nice to figure out.

One of the exhaust guys put it up on the lift and said that someone replaced the rear cat and bored through the front, so it's toast and probably the reason for the code.

But it would be nice if someone can tell me what the data means.
 
  #16  
Old 03-11-2019, 08:23 AM
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Here's the definitions for the mode 6 self test data that you posted.

https://gsi.ext.gm.com/gmspo/mode6/p...20final_dm.pdf

OC60 is the test for the cat converter that is failing and setting the P0420. Doesn't really tell you anything that you didn't already know.

Now take Torque Pro and plot both B1S1 and B1S2 O2 sensors on the same graph (don't think Car Gauge Pro will let you plot two at a time). If the two O2 sensors are cycling pretty much the same frequency, your cat is junk.
 

Last edited by LesMyer; 03-11-2019 at 08:33 AM.
  #17  
Old 03-11-2019, 08:41 AM
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Originally Posted by LesMyer View Post
Here's the definitions for the mode 6 self test data that you posted.

https://gsi.ext.gm.com/gmspo/mode6/p...20final_dm.pdf

OC60 is the test for the cat converter that is failing and setting the P0420. Doesn't really tell you anything that you didn't already know.

Now take Torque Pro and plot both B1S1 and B1S2 O2 sensors on the same graph (don't think Car Gauge Pro will let you plot two at a time). If the two O2 sensors are cycling pretty much the same frequency, your cat is junk.
Thanks for the chart, very informative, i'll try that with torque pro, I have both, car gauge is more user friendly thats why i use it more often, but i'll try graphing the two together on torque pro

Thank you
 
  #18  
Old 03-11-2019, 08:45 AM
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Originally Posted by FUN-V View Post
Thanks for the chart, very informative, i'll try that with torque pro, I have both, car gauge is more user friendly thats why i use it more often, but i'll try graphing the two together on torque pro

Thank you
You're welcome. Give us a screen capture of the plots at steady 2000 rpm in park .

 
  #19  
Old 03-11-2019, 08:49 AM
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Here's a video of what you will be doing. This guy's scan rate for his equipment kind of sucks, but you get the idea. The front sensor cycles and the other doesn't so much.

Hey it would be useful and very interesting to post before/after plots of the O2 sensor voltages on the same vehicle (if you end up installing the new cat)! Then people can see exactly how to do the diagnosis.

 

Last edited by LesMyer; 03-11-2019 at 09:08 AM.
  #20  
Old 03-11-2019, 06:34 PM
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lesmyer, will do, probably post on wed.
 

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