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I have replaced all 4 O2 sensors and the CEL is still on. The code reads bank 1 sensor 2. I know which one that is, but don't know what is wrong with it. Please Advice
 

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Q: After replacement, did you either have the CEL codes cleared from the ECU via an OBD scanner or disconnect the negative battery cable for a few minutes to erase the codes from memory?

Q: What brand/model oxygen sensors did you replace the old ones with?

Q: What codes are being thrown now?
 

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Uhhh.... Bank 1 sensor 2 is po420... The first thing I do when I see that code is replace o2 sensor. If still on cat is bad;)
Where did the OP state that the CEL code was P0420??? Are you reading something I'm not? Bank 1, Sensor 2 is also referenced via the P0037, P0038 and P0136 codes. :dry3d:
 

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...But I bet bank 1 cat is bad. Just a hunch:)
$1 says he installed Bosch sensors as replacements. ;)

I've yet to see a BXS2 code indicate an actual failed cat. It's an easy dealer ripoff. Unless you throw all kinds of chemicals/cleaners/octane boosters/etc into your combustion stream, physically damage the cat assembly, or fail to correct a bad misfire, they generally will last as long as the vehicle. What usually causes the CEL is a burnt out heater circuit/element in the oxygen sensor component itself.
 

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$1 says he installed Bosch sensors as replacements. ;)

I've yet to see a BXS2 code indicate an actual failed cat. It's an easy dealer ripoff. Unless you throw all kinds of chemicals/cleaners/octane boosters/etc into your combustion stream, physically damage the cat assembly, or fail to correct a bad misfire, they generally will last as long as the vehicle. What usually causes the CEL is a burnt out heater circuit/element in the oxygen sensor component itself.
I must be wearing postourpedic shoes because I stand corrected:clown: I have to agree with you that if these are Bosch then the computer doesn't like em. If denso, IDK? Because I can't see them having a problem

Where is the OP? I gotta know now. I'm super curious.

Oh ya, I take my bet back you make a good point.:D
 

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p420 is cat insufficiency. I get it all the time, its thrown from the rear o2 sensors. Basically your cat's are no good. Mine did this for months, o2 reading too hot, caused misfire... Dealer couldn't figure it out. Ended up being ALL the cats where burnt out.

ON the GEN 2's front 02 sensors are wideband and rear being narrow band. The ECU has to calibrate the front o2 wide-band, when it does this it compares it to the rear o2's.
 

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p420 is cat insufficiency. I get it all the time, its thrown from the rear o2 sensors. Basically your cat's are no good...
Cater~

If you get it "all the time", the last thing I would be deducing is that your cats are failing. Catalytic converters are robust, static constructs. You really have to make an effort to actually damage one. Your conclusion that "all the cats were bad" leads me to conclude that you simply got hosed by your dealer service writer.

This code will also be present when the sensor component itself is giving aberrant readings. Remember: the downstream sensors ONLY give electronic measurements of inferred hydrocarbon/oxygen ratio readings further inferring catalyst inefficiency. When your measuring stick is kaput, the rest of your conclusions based on that function are junk.

Oh, and catalyst efficiency -- or lack thereof -- does not cause misfires.

Keep that in mind when you post up on some board that the OP should hump his way to his dealer for a $1,400 per cat service trip.
 

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Cater~

If you get it "all the time", the last thing I would be deducing is that your cats are failing. Catalytic converters are robust, static constructs. You really have to make an effort to actually damage one. Your conclusion that "all the cats were bad" leads me to conclude that you simply got hosed by your dealer service writer.

This code will also be present when the sensor component itself is giving aberrant readings. Remember: the downstream sensors ONLY give electronic measurements of inferred hydrocarbon/oxygen ratio readings further inferring catalyst inefficiency. When your measuring stick is kaput, the rest of your conclusions based on that function are junk.

Oh, and catalyst efficiency -- or lack thereof -- does not cause misfires.

Keep that in mind when you post up on some board that the OP should hump his way to his dealer for a $1,400 per cat service trip.

I got that code all the time because My CATS WHERE Burnt out. Well Three of the four. I get it now, because I cut the two rear cats off and replaced the front two with Highflow cats. Worked good for 1000 or so miles, again the code. I haven't had time to put the o2 Sensor emulator on yet. I Don't use a dealer, normally. I have been trying but its my experience all dealer techs are incompetent in this part of the country. Having a full shop at my house, Minus a CNC Lathe I tend to do every-thing here. which included replacing full exhaust.

I've burned three out on the tundra, Two on a Mustang Cobra

On the second generation tundra, when the cats are faulty, I.E Exhaust temp's too high ECU cuts fuel, in effect creating a misfire.
 

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p420 is cat insufficiency. I get it all the time, its thrown from the rear o2 sensors. Basically your cat's are no good. Mine did this for months, o2 reading too hot, caused misfire... Dealer couldn't figure it out. Ended up being ALL the cats where burnt out.

ON the GEN 2's front 02 sensors are wideband and rear being narrow band. The ECU has to calibrate the front o2 wide-band, when it does this it compares it to the rear o2's.
I knew it!!!! The front 2 sensors calibrate to the rear!!! Everyone thought I was crazy. I put 02 sims on my truck after my Magnaflow high flows burnt out. Instead of getting a 420/430, I got the code for the front 02 sensors. I replaced all 4 sensors and still got a code for the front 02's. I then took off the sims and cleared my codes with my scanner. A little while later I got 420/430 again.

I just said eff this, I'm takin the cats out and living with the check engine light.
 

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escondidotundra : Way I understand the URD 02 emulator suppose to allow calibration.

Remmy700P: You cali people crack me up with you smog, emissions stuff. I'm sure he knows some one.
 

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Yeah cali is tough. Unfortunately a lot of people think PO420 or 430 automatically means "I need a new cat", and therefore buy the dealer replacements.

I just had JBAs installed and am getting both codes. But these sensors work in concert with the computer. THEY set the MIL off 9 times out of 10. Not the catalytic converters.

If you live in California, always replace downstream O2 sensors first. Great thread!

Derek
 
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