OK. Here is a quick back story. Car was jerky, cleaned EGR valve and plat. Still a little jerky and would not get into lean burn. Replaced both primary and secondary o2 sensors. Now I can do lean burn but get P0420. I bought a new secondary o2 sensor and still get a P0420.
I do not see or hear any holes around the cat or engine.
Top of the CAT looks OK form the primary sensor opening.
What else could be casing the P0420 code?
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2000 MT Insight New Formula Red Picked up 2010/07/23
2000 MT Insight New Formula Red Picked up 2012/01/13
2006 Prius Barcelona Red Package #7. Picked up 2006/01/02
Converted to Plug-In on 2008/08/12 with Hymotion L5
I did read a thread on the forum about someone who had herky jerky issue, replaced EGR valve, cleaned the EGR plate but still had issue. He ended up replacing the CAT and found that the old one/ones were clogged up causing high back pressure in the exhuast system. Not saying this is the issue but just something to think about. The code you are getting seems to imply a failed CAT.
I don't know of any kind of back pressure testing, I did look into my CAT when I replaced my upstream O2 sensor, I could see the screens and everything looked normal inside of it, at least what I could see. I guess if I took it out you would be able to look into the pipes and see if the screens are blocked or deteriorated.
Maybe someone on the forum knows of a good way to check the CATs.
It can be done but is a little complicated. (Its the pressure difference from the intake side and the exhaust side of the cat.) It's easy to check the second cat. Remove the exhaust system right at the cat. If the cat screen shows a gray color, you are probably OK. If it is a darker color than gray, it "might be partially obstructed". There was a recall on the ECM indicating a false bad cat was't there?
Clear the code and see if it returns. Something about the ECM doing a relearn after the O2 replacements.
HTH
Willie
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01 5 speed. "Little Red Rocket"
The first "TURBOCHARGED" Hybrid, (01/2003)
296,000 mi. @ 58.0 LMPG
2007 Honda Fit, Red Sport AT
1998 Ford F-150, NASCAR "Limited Edition"
(3K made, possibly the prototype one)
I've reset multiple times and still get the P0420. I think I can remove the secondary cat without too much trouble but the primary is rusted so bad to the bolts that go to the engine block I would have to replace the whole thing. If I get another warm day I might take a look at the second cat.
Would running the car without the second cat and muffler throw any more codes? The reason I ask is that if I can drive the car without them and it does not throw a P0420 code then I would know its the secondary cat right?
__________________
2000 MT Insight New Formula Red Picked up 2010/07/23
2000 MT Insight New Formula Red Picked up 2012/01/13
2006 Prius Barcelona Red Package #7. Picked up 2006/01/02
Converted to Plug-In on 2008/08/12 with Hymotion L5
Not sure about actual cat failure, but just got rid of the P0420 code on mine with the recall. To my great surprise and pleasure, Honda put in a new programmable ECM under the recall, even though I knew it was a goodwill thing by this time, given I have a 2001 model. I am very sure my cats are ok, but have no way to test them.
However, before I got that, I used the mod I found through a link on this forum using two (2) anti-fouler adapters on the secondary O2 sensor. Drove it this way for two months and did not get a code, and the code came back in two days after I removed this mod. (I was getting the herky jerky motion sometimes that I was thinking was an EGR problem, so I wanted to remove the mod and make sure.) I then took the car to the dealer for the recall.
You drill out the first anti-fouler adapter to just clear the O2 sensor (and still leave the threads on the adapter), and screw this anti-fouler into another one. Put that assembly into the downstream hole on the engine cat (my car only has two sensors), and put the secondary O2 sensor into that.
Well I went to the dealer and they think I dont have the correct ECM. The documents for the car did not say or clearly say the service bulletin was done. I'll have to check the ECM part number and report back.
A new ECM is about $500 from the dealer if I need one.
__________________
2000 MT Insight New Formula Red Picked up 2010/07/23
2000 MT Insight New Formula Red Picked up 2012/01/13
2006 Prius Barcelona Red Package #7. Picked up 2006/01/02
Converted to Plug-In on 2008/08/12 with Hymotion L5
Tell them to go take a hike, the ECM update is a TSB. It's free if it hasn't been done yet.
Even if you do need a new ECM, which you don't, there's no point in buying a brand new one. Contact Brent at Flamboyant auto parts and get a used one.
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Insight #2 - Silver '01 5MT @ 450,000 as of 1/12 - Best Tank: 86.0MPG over 800mi
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P0420 code. Need Help.
