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Discussion Starter · #1 ·
Intermittently seeing a constant CEL being on, it goes away and then comes back.

Scanned the code and it's showing P0420 - very common I believe on the Hondas?

No performance issues and MPG are between 19-21, should I be concerned or just continue to drive it? Thank you for the help :)
 

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Yes. Immportant to solve. Start simple.
  1. New Air filter.
  2. Have you ever cleaned the MAF? Remove and spray short bursts of CRC Electronic Cleaner or MAF into the electrodes. Let dry thoroughly, reinstall.
  3. Inspect air intake tube for cracks. Clamps secure.
 
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Discussion Starter · #5 ·
Yes, I did see some cracking on the intake tube and has been patched with some tape - could that be the reason or culprit?
 

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Yes, I did see some cracking on the intake tube and has been patched with some tape - could that be the reason or culprit?
I'd replace. This part is AWD/2wd sensitive.
142636

New air intake tube with clean MAF and air filter will probably end the codes.
 
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Discussion Starter · #8 ·
Thank you all, planning to inspect air filter first, then clean MAF using CRC elctronic cleaner. If code didn't go away, replace the tube and air filter.

Can spark plugs be the reason for it or would be a different code?
 

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Yes, I did see some cracking on the intake tube and has been patched with some tape - could that be the reason or culprit?

If the tube is cracked, you really should replace it even if someone Jim-Bobbed it.

 

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Thank you all, planning to inspect air filter first, then clean MAF using CRC elctronic cleaner. If code didn't go away, replace the tube and air filter.

Can spark plugs be the reason for it or would be a different code?
If the air intake tube is cracked, it is very much a priority to replace. It distorts MAF reading.
Bad spark plugs usually trigger misfire codes.
 

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While the air tube is important to fix, it will not set a cat. performance code. The code is set based on the air/fuel ratio either in the cat or existing the cat. It uses the pre cat a/f sensor readings to determine what the post cat reading should be. False 420/430 codes are rare in Honda's.
 

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While the air tube is important to fix, it will not set a cat. performance code. The code is set based on the air/fuel ratio either in the cat or existing the cat. It uses the pre cat a/f sensor readings to determine what the post cat reading should be. False 420/430 codes are rare in Honda's.
The hope is, with a correct airflow reading, the excessive amount of fuel going into the engine will stop and what is unburned will no longer be digested by the cats. Hopefully before cat failure occurs and they perform well enough for the emissions codes to disappear.
 

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In a mass air veh, unmetered air causes a lean condition, not a rich condition. If the mass air doesn't measure the air, it doesn't exist to the pcm. If the pcm doesn't see it, then it doesn't add more fuel, giving you a lean condition. Either way, rich will not give you a cat code. Since the mid 90s(on many models), Honda uses a true a/f sensor, so it knows the exact a/f ratio entering the cat. It will set a rich/lean code, not a cat code. Cat codes are set when the ratio is off entering/existing the cat. Don't suppose you could tell me the location of the mass airflow sensor on an 07 pilot?
 

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P0420
^^^ read my post here ^^^
Your cat efficiency codes are thrown because the AF sensor and O2 sensors are "telling" the computer that your cat isn't working. These sensors will fail long before a cat does in a properly maintained and well running engine. If you're burning coolant or oil then your cats may be permanently damaged along with the sensors. Just know a code thrown is only as reliable as the sensors that trigger it. For the Pilot, the 420 code is for the REAR converter near the firewall and the 430 code is the front near the radiator.
 

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In a mass air veh, unmetered air causes a lean condition, not a rich condition. If the mass air doesn't measure the air, it doesn't exist to the pcm. If the pcm doesn't see it, then it doesn't add more fuel, giving you a lean condition. Either way, rich will not give you a cat code. Since the mid 90s(on many models), Honda uses a true a/f sensor, so it knows the exact a/f ratio entering the cat. It will set a rich/lean code, not a cat code. Cat codes are set when the ratio is off entering/existing the cat. Don't suppose you could tell me the location of the mass airflow sensor on an 07 pilot?
So would it be a correct statement to say if one keeps their air filter clean, vacuum leaks in check and the fuel air mix perfect, you are in effect, extending the life of your cats?
 

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Your cat efficiency codes are thrown because the AF sensor and O2 sensors are "telling" the computer that your cat isn't working
So that's why I have multiple customers that come in from other shops with all 4 new a/f sensors and still setting cat codes. It's been proven many times that Honda's don't set false cat codes. Honda is very good at knowing that the sensor is out of spec vs cat efficiency below specs.
 

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So would it be a correct statement to say if one keeps their air filter clean, vacuum leaks in check and the fuel air mix perfect, you are in effect, extending the life of your cats?
Contamination is the main killer of cats, burning coolant or oil being the main ones. Once the cat can no longer store enough oxygen, it's done. Extremely rich will can generate enough heat to destroy it as well.
 

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So that's why I have multiple customers that come in from other shops with all 4 new a/f sensors and still setting cat codes. It's been proven many times that Honda's don't set false cat codes. Honda is very good at knowing that the sensor is out of spec vs cat efficiency below specs.
Every vehicle is unique because they are all used and maintained differently. I wasn't the person who did diagnostic work on your customers vehicles, only on my own so I can only explain my thought process in diagnosing my vehicle's P0420 code and hope to possibly save someone some time and money in unnecessary parts replacements.
How would you explain to a customer why, after replacing their catalytic converter, their check engine light came back on with the exact same code, especially after explaining to them that Hondas don't set false codes.

Replacing sensors blindly hoping it will solve the problem is just as bad as blindly replacing components expecting the same results. Converter contamination is a real problem and I believe it because most people don't know how or can't afford to maintain their vehicle.
 

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Contamination is the main killer of cats, burning coolant or oil being the main ones. Once the cat can no longer store enough oxygen, it's done. Extremely rich will can generate enough heat to destroy it as well.
Thanks.
So what maintanance can we do to extend the life of our cats?
 
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