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
Anyone ever buy from here? This matches the passenger side cat 4CRXV03.5VMO
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.
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?
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.