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Hello,

I am dealing with a PO420 issue and trying to do the citric acid soaking but wanted to check the sensors before I started... I bought a pretty pricey ($185) OBD scanner (Zurich ZR13) at Harbor Freight. It does everything SRS. ABS, Live data, etc.

Anyway, the upstream O2 sensor is reading in milliamps and not volts. At idle it bounces around .00 and sometimes shows -.00. When I am driving it it bounces all around .20, .40. Catalytic sensor reads in Volts. Thinking this was my 420 problem, I bought/installed a new Denso sensor but it still reads the same. Thinking it might be something with the ODB reader, I tested the readings on my 2010 Infiniti and both O2 sensors read in volts.

BTW: the cat sensor bounces around 550 - 700. Car runs awesome. Smooth idle, good acceleration, good MPG. I brought it to the dealer and spent $117 for a complete diagnostic. They came back with two things: I need a new Catalytic converter ($1,400) and the AC fan was noisy ($100). I Bought the car for my daughter (106K miles on it) and she will be driving to FLA next month - 13 hours each way. If the citric acid thing does not work and I am really torn about spending the $$ if the car runs great otherwise.

Appreciate any help.

Rich
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The up stream "O2" is not an O2 sensor, actually different though looks like it. Honda does things differently, its not a scanner problem, its how Honda has designed reading the information for the computer to adjust fuel ait mixture.

0420 is one of only 2 things ever. The rear 02 sensor or the catalytic converter.

Hondas are VERY finicky about the converter.

Very easy fix is buy one of the O2 adapters which moves the 02 sensor out of the converters direct flow. Doesnt fix it 100% of the time, bit for $6 its worth a shot.

Also, a 0420 code is of zero concern for driving it as long as there is good flow out the tail pipe.

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My 2010 CRV's check engine light is on and I have the P0420 code. O2S1 is reading 0 mA and the lambda ratio jumps between -0.99 and 0.99.

Cat temp bank 1 reads 967.3 F.

Unfortunately my ELM327 doesn't provide any data for O2S2.

There hasn't been a change in my car's gas mileage and I haven't noticed any odors at the tail pipe.

Tigris99 suggests that it is likely 1 of 2 problems for Honda's: the catalytic converter or the rear O2 sensor. Why not the front O2 sensor?

I welcome your ideas for how to solve this problem.
 

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put one of these on and the light will stay off I have done about 8 vehicles including on a S10 4.3 with a gutted converter only use it on the downstream O2 I did do a chevy aveo that i needed to stack 2 to keep the light off I think because the converter is basically at the engine but as long as its not restricted this works and not EPA approved https://www.ebay.com/itm/O2-OXYGEN-...8-x1-5-BUNG-HHO-ADAPTER-OBD2-02-/141410935430
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it spaces it out of the stream and holds oxygen in the area just like a good converter does it stores oxygen,the environmental people don't like it so be careful who you tell some get bent out of shape,the downstream o2 just reads converter efficiency for emissions,the front o2 is ok lambda 1 is good that means the fuel trim is close to 0% 14.7 to 1 air fuel mixture ,where it should be but for a p0420 its the converter almost always unless there is an exhaust leak before the converter
 

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it spaces it out of the stream and holds oxygen in the area just like a good converter does it stores oxygen,the environmental people don't like it so be careful who you tell some get bent out of shape,the downstream o2 just reads converter efficiency for emissions,the front o2 is ok lambda 1 is good that means the fuel trim is close to 0% 14.7 to 1 air fuel mixture ,where it should be but for a p0420 its the converter almost always unless there is an exhaust leak before the converter
hi would this work on 2016 civic 1.6idtech, im in uk, im getting cel for post cat o2 ?
 
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