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Discussion Starter · #1 ·
About 5 months ago my wife's 2004 Santa Fe CEL came on. I downloaded the codes and had a P0431 and another I cant remember. After doing some research on the forums I found out that there was a possibility that she could of had a misfire. The car at that time had about 150k on it. I changed the plugs and the coil packs. I noticed immediately that the car seemed to run cooler as I didn't smell the engine as much anymore. When I say smell I mean the antifreeze smell. She had a hose spring a leak a few months ago and since then I would occasionally smell the engine when I walked into the garage. I had washed the engine down good but it occasionally would still have that smell.

After changing the plugs and coil packs I cleared the codes and I haven't had any issues since June. This weekend we drove to Yellowstone from Utah (about 6 hours) and the code came on shortly after arriving in Yellowstone. I couldn't find anyone that would help me in Jackson Hole so we kept our fingers crossed and enjoyed our 2 day trip.

We came back today and as soon as I got home I checked the codes and P0431 is back. There are no performance issues and in fact we got exceptional gas mileage (28mpg) during the trip. My research is telling me it is the catalytic converter and I don't mind changing it but wanted some opinions before diving in.

1. The cats are original (we bought the car new in 2004)
2. Should I change the O2 sensors first?
3. How many O2 sensors are there?
4. Is there a way to test the sensors (I have a diagnostics reader and can read them in real time but just not sure what I am looking for).
5. Is it really true that there are 3 cats on this car (2 monitored and 1 not). Should they all be changed or just bank 2?

Any help at all would be truly appreciated.

Thanks

Glenn
 

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Misfire somewhere stress the cat, lost efficiency as determined by Ox sensor toggle.

GDS in current data, select ox sensors for respective cats, select graph mode and watch sensor activity.
 

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Discussion Starter · #3 ·
what am I watching for on the sensor activity? I am able to run a live data and see various numbers just not sure what they mean. I ran the o2 sensor test and received the following:

B1S1
B1S2
B2S1?
B2S2

I also ran the Live Data like you suggested and noticed that for B1S1 there was a steady pattern like a heart beat. The B1S2 had a ? beside it and it was all over the place with no pattern. B2S1 had a "G" beside it and had a steady pattern like a heart beat. B2S2 had a sometimes steady pattern but also erratic pattern.
 

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I dont have picture on home PC,, it on work PC..

S1 should be active toggle .1v - .7/.8v and back forth,, the S2 should lay flat line voltage, unless throttle snapped and voltage shift some or spike and return.

If S2 "mirrors" S1 for activity, then good sign the brick in between the 2 is not there to buffer the second sensor.. S1 is fuel trim for exhaust as it come out of cylinder prior to hitting the cat,, S2 is used for cat efficiency monitoring purpose.
 

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Discussion Starter · #5 ·
Sorry for the lack of understanding but I am a little confused. Is the 4 sensors or 2. I take it from the readings there are 4 (2 for b1 and 2 for B2).

If I understand you correctly then according to the Live data B2 S1 and S2 are responding the same way which would indicate that there is no buffer and that the cat is not working like it is supposed to or perhaps one of the sensors is bad.

Would that be a correct assumption.

I am more accustomed to working on jet engines but I have worked on my share of cars/motorcycles but these exhaust systems and sensors really do make troubleshooting difficult. Thanks for the assistance.
 
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