P0420 Catalytic Converter OBDII O2 Readings - DodgeIntrepid.Net Forums - Dodge Intrepid, Concorde, 300m and Eagle Vision chat
 
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post #1 of 4 (permalink) Old 06-10-2015, 12:24 AM Thread Starter
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P0420 Catalytic Converter OBDII O2 Readings

Hi all,

First post for me. Hopefully this is the right area. I bought a 04 Intrepid SXT 8 months ago and have had a few issues with it, but overall love the car. First issue was a P0441 Evap purge system leak which was around a $400 fix with smoke test. Now I'm getting the P0420 Catalytic Converter efficiency error. I want to confirm that this is in fact a catalytic converter issue and not something that would be fixed by the well-known defouler/O2 spacer fix.

My understanding is that the front and rear O2 sensors read the oxygen levels before and after the cat. Ideally with a good cat the front O2 sensor should be widely changing from low to high voltage. The rear should remain somewhat stable if the cat is doing it's job.

I recorded a bit of what I was seeing with the O2 sensors on the Torque application on my Android (attached). The O2 1x1V and O21x2V are the front and rear sensors of bank 1 respectively. As you can see the rear O2 sensor is varying almost as wildly as the front, as if the cat isn't even there. When comparing to O2 2x1 O2 2x2 I can see the rear O2 sensor from bank 2 is much more stable. Does this look like a bad cat? Sure seems like it to me? What are your thoughts.

Additionally, I heard the universal cats aren't great on Chryslers. Any truth to this? I was able to find a direct fit cat on catalyticconvertersonline.com
(catalyticconvertersonline.com/p-dodge-intrepid-catalytic-converter-california-obdii-california-obd-ii-direct-fit-replacement-catalytic-converter-104754)
Anyone ever buy from here? This matches the passenger side cat 4CRXV03.5VMO

Thanks all!
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post #2 of 4 (permalink) Old 06-10-2015, 02:58 AM
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Doesn't look like that catalytic converter is doing much. I reckon I will go ahead and clarify that it IS a catalytic converter issue, but if you don't have any driveability problems then it likely IS something that a de-fouler/non-fouler/spacer can "fix". Really, the non-foulers do not fix the actual problem but just hide the symptom (by moving the sensor out of the direct exhaust stream) so it doesn't show up as a fault code. Its a cheaper and simpler alternative to replacing the catalytic converter but I'm not sure that your vehicle will pass your annual emissions testing considering you say that you live in California.
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post #3 of 4 (permalink) Old 06-10-2015, 06:19 PM Thread Starter
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Thanks BH1992. That's a good point, I would rather fix the problem than just mask it. I don't notice any changes in how the car drives although it could have had this problem when I bought it. I do seem to be getting worse gas mileage; however, which could be a symptom of this.

As for the replacement cat. Any experience with purchasing direct fit cats? Anyone have any issues with the universal ones?
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post #4 of 4 (permalink) Old 06-10-2015, 06:21 PM Thread Starter
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I guess the main reason I ask is I heard replacing the cat is a pain with hand tools. I was going to take it into the shop which quoted me $1300 for the factory cat and installation. The direct fit cat itself is $800. Another shop would do it for $650, welding in a universal. I found the direct fit cat on that catalyticconvertersonline site for only $270 which seems like too sweet a deal to be true.
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