P0420 Help please.

Cw370TT · 05-04-2016, 02:22 PM

So I've got the p0420 Cat effic. Below normal bank 1. Hooked it up to the scanner and decided to check the o2'status. Bank 1 AND 2 o2 sensors position 1 AND 2 will not read. In case I didn't say that right the o2 sensors at the rear on both sides will not rwad. The ones in the front will read and fluctuate. The 2 rears on both sides read 0 with zero fluctuation. What's going on here? Is it Cats? O2 sensors. Or something electrical idk. Thanks for any insight!

Oh and at the moment I can't search the forums on my phone. I can do google but mostly all I find is replace a cat but in my case looking at 2 sensors that won't read on both banks. These are position 2!

Array · 05-04-2016, 02:49 PM

Have you replaced your cats recently or taken them off? Also it may be worth swapping each banks to see how they react on opposite sides, otherwise they both may be dead, not sure on the likelyhood of that

Cw370TT · 05-04-2016, 03:09 PM

Haven't touched the cats. No mods. I have the car jacked how the hell do you get to the front o2's. Dear God lol!

Jhill · 05-04-2016, 07:18 PM

Not sure I would be trusting your scan tool data. In order to get a p0420 your rear o2 would need to have fluctuating voltage which would indicate the cat has failed (rear o2 mirroring front AF sensor). Not to say it isn't possible but I have never seen a gasoline obd ii car have a p0420 and not have it be a bad cat. The manufacture is pretty tight on having all other monitors check and pass before throwing a p0420 (think about it, it's an extremely expensive part with quiet a long warranty so the manufacture does not want to be covering it unless they absolutely have to). Diesel is a different story, if the regen injector clogs and doesn't spray fuel into the cat to get it hot enough then they will throw a p0420 but gasoline doesn't have any systems like that to fail before the cat.

05-04-2016, 02:22 PM	#1 (permalink)
Cw370TT Base Member Join Date: Apr 2016 Location: Georgia Posts: 24 Drives: 09 370 Sport 6MT Rep Power: 9	P0420 Help please. So I've got the p0420 Cat effic. Below normal bank 1. Hooked it up to the scanner and decided to check the o2'status. Bank 1 AND 2 o2 sensors position 1 AND 2 will not read. In case I didn't say that right the o2 sensors at the rear on both sides will not rwad. The ones in the front will read and fluctuate. The 2 rears on both sides read 0 with zero fluctuation. What's going on here? Is it Cats? O2 sensors. Or something electrical idk. Thanks for any insight! Oh and at the moment I can't search the forums on my phone. I can do google but mostly all I find is replace a cat but in my case looking at 2 sensors that won't read on both banks. These are position 2!

05-04-2016, 02:49 PM	#2 (permalink)
Array Enthusiast Member Join Date: Jun 2014 Location: home.jpg Posts: 286 Drives: '12 Pearly White Rep Power: 10	Have you replaced your cats recently or taken them off? Also it may be worth swapping each banks to see how they react on opposite sides, otherwise they both may be dead, not sure on the likelyhood of that __________________ 2012 370z 7AT- ES2 with PSS, K&N Drop-ins, LED's all around, Berk HFC, FI CBE non-res, KW V1's 2003 A4 5MT- The Beater

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05-04-2016, 03:09 PM	#3 (permalink)
Cw370TT Base Member Join Date: Apr 2016 Location: Georgia Posts: 24 Drives: 09 370 Sport 6MT Rep Power: 9	Haven't touched the cats. No mods. I have the car jacked how the hell do you get to the front o2's. Dear God lol!

05-04-2016, 07:18 PM	#4 (permalink)
Jhill Track Member Join Date: Mar 2016 Location: San jose Posts: 846 Drives: 2013 370z sport Rep Power: 3384	Not sure I would be trusting your scan tool data. In order to get a p0420 your rear o2 would need to have fluctuating voltage which would indicate the cat has failed (rear o2 mirroring front AF sensor). Not to say it isn't possible but I have never seen a gasoline obd ii car have a p0420 and not have it be a bad cat. The manufacture is pretty tight on having all other monitors check and pass before throwing a p0420 (think about it, it's an extremely expensive part with quiet a long warranty so the manufacture does not want to be covering it unless they absolutely have to). Diesel is a different story, if the regen injector clogs and doesn't spray fuel into the cat to get it hot enough then they will throw a p0420 but gasoline doesn't have any systems like that to fail before the cat.