Rep Power: 0

Ok thanks for the information and the help. So greatly appreciated

 
Rep Power: 0

Well just an update. Got the timing belt replaced as well as the water pump, serpentine belt, and p/s belt. All went well now that all that has been replaced and car running well my check engine light came on and now throwing out a P0420 code. This is a new code as it never showed up before. Any info or help would be greatly appreciated.

Thanks much in advance.

 
Rep Power: 222

Cat code, could be from all the starting attempts. Clear it, do a few good highway drives to get everything nice and hot and see if it comes back?
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Rep Power: 210

AutoZone A/F sensor probably is not oem Denso/NTK/NGK sensor. This car (ecu) is very particular about the correct factory oem make and model A/F sensor, and maybe the cause of the code?

Call the AutoZone you purchased it from and ask them to verify the manufacturer. AutoZone just rebrands a lot of their parts under the Duralast name so you have to try to get them to be specific (if possible) of who is the true Original Equipment Manufacturer (OEM).

For future reference it's best to buy from online oem dealers like HondaPartsNow, Majestic Honda, or local dealer parts department rather than from chain autoparts stores.

 
Rep Power: 222

Didn't realize you had swapped out the a/f sensor. Yeah make sure it's Denso or ntk

 
Rep Power: 0

Hello

thanks for the replies. Yes the A/F sensor I bought from Advance Auto was a Denso sensor. I work 35 miles from where I live and have cleared the code 2 times since and still comes back on.

Again thank you all for your help and replies. Greatly appreciated as always.

 
Rep Power: 222

How quickly does it come back?
could just be coincidence that the cat is failed

 
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Maybe a day and a half of driving.

 
Rep Power: 222

You can try a bottle of catalyst cleaner, it may help. If not the cat is done anyways

 
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Hello. Ok just an update and some stats if they matter.

I have added a bottle of catacleaner to the fuel per instructions (1/4 tank or minimum of 4 gallons, drive 10-15 miles under normal driving conditions then fill up tank). However after adding the cleaner I was in a lot of stop and go traffic that day. After filling the tank I reset the code. 22.9 miles later (next morning) light came on again, same code. Before the code would come on around 45-55 miles after resetting.

now I googled symptoms of bad converter and I have none of these symptoms listed below. Actually I have just the opposite as things seem better then before

symptoms:

• Sluggish engine performance.
• Reduced acceleration.
• Dark exhaust smoke.
• The smell of sulfur or rotten eggs from the exhaust.
• Excessive heat under the vehicle.

also I saw another symptom of poor gas mileage. I averaged before between 34-40 mpg prior to all this mess per an app I have on phone. When I filled up yesterday I was at 37.4 mpg.

now I’m wondering if maybe me being in stop and go traffic before filling up if that may have had an impact of the cleaner not working properly and should I get another bottle and try again but in less traffic and at more normal driving conditions.

 
Rep Power: 224

I have had the P0420 fault on my Civic for roughly 6 years. It does not cause any of the symptoms you've listed above although it is possible. If you don't have emissions testing in your area and don't care if the check engine light is on all the time then don't worry about it. Otherwise you can try replacing the secondary o2 sensor with an OEM one first before replacing the cat.

If you're talking about P0135 fault that's a different story.

 
Rep Power: 222

That's why I suggested driving on the highway.
and it will throw the code without any of those symptoms, the computer is very picky. Which is why cheap aftermarket converters don't last long in these cars before throwing the code again because the computer thinks it's "bad"

 
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well I was actually on an interstate after putting the cleaner in but there was an accident so it was stop and go for about 7 miles. I didn’t clear the code until after I did the 10-15 mile cleaning. I did it after I filled the tank. I will try another bottle this weekend when there is less traffic and clear the code before I drive the 10-15 miles. I am pretty sure it’s the original converter. But I certainly won’t buy aftermarket converter either.

I may also too replace the downstream O2 sensor as well since I’m sure that’s probably original and I’ve already replaced the upstream

 
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No it’s the P0420 code giving me the headaches lol. We do have emissions testing but not due for another year and a half. I’m thinking of replacing the other sensor now this weekend and trying another bottle of cleaner as well.