2007 Accord - P0420 Code

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My occasionally driven 2007 accord with AT and ~154K miles - yesterday filled up the gas tank and after an hour or so drive, randomly started to throw up CEL. 28-30 or mpg are normal, through manual calculation and no performance issues. Scanned it today and it was P0420 code, should I add techron and give it a try? Or any other inputs and advise? Thank you thumbsup
 
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Originally Posted by maverickfhs
My occasionally driven 2007 accord with AT and ~154K miles - yesterday filled up the gas tank and after an hour or so drive, randomly started to throw up CEL. 28-30 or mpg are normal, through manual calculation and no performance issues. Scanned it today and it was P0420 code, should I add techron and give it a try? Or any other inputs and advise? Thank you thumbsup
Cataclean. Just before your next smog check.
 
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They showed me Cataclean today on AZ and thought it's a snake oil? Can I drive it as-is and won't do any major harm? Don't drive it everyday.
 
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Originally Posted by maverickfhs
They showed me Cataclean today on AZ and thought it's a snake oil? Can I drive it as-is and won't do any major harm? Don't drive it everyday.
I have pulled that P0420 code before. Catalyst below threshold. It does not seem to hurt anything other than your pocketbook when needing to pass a smog check.
 
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Either the cat is bad, or the downstream oxygen sensor is too dirty to work well any more. On the CataClean thing, I didn't know that existed. Nice idea for a product. Might work, who knows? Does seem like the zylene, acetone, and alcohol would just oxidize in the combustion chamber, leaving little to no solvent to cleanse the cat.
 
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P0420 won't hurt anything other than annoying you with the CEL. My 2003 has one that comes and goes seemingly at random. I haven't been bothered enough to do any investigating on it as the fuel trims are fine, so the upstream AF sensors are working just as they should. Like others have said, its probably a lazy cat or downstream O2.
 
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I'll start with techron or Berryman and an italian tune up and see if it takes care of it. I literary drive like a grandpa laugh
 
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Originally Posted by maverickfhs
My occasionally driven 2007 accord with AT and ~154K miles - yesterday filled up the gas tank and after an hour or so drive, randomly started to throw up CEL. 28-30 or mpg are normal, through manual calculation and no performance issues. Scanned it today and it was P0420 code, should I add techron and give it a try? Or any other inputs and advise? Thank you thumbsup
I have 2 of these vehicles. Main problem is these vehicle has oil consumption problem. It burns oil and the oils gets trapped in the catalytic converter. If you get lucky, you can clear the CEL, and it might not come back on. You can try the GUMOUT Complete Fuel System cleaner and drive it until empty, it may help temporary.
 
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Thanks, any idea if O2 sensors can be cleaned one by one? Does Bank 1 means, downstream sensor? Because I can clean it and see if it fixes CEL and then replace it. Yeah I'll unhook battery negative and then see if CEL comes back too.
 
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Don't bother with the O2 sensors.....The odds of having one emulate a faulty Catalyst is astronomical. Run a 18mm Antifouler on the O2 behind the Catalyst & move on with life.
 
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Originally Posted by clinebarger
Don't bother with the O2 sensors.....The odds of having one emulate a faulty Catalyst is astronomical. Run a 18mm Antifouler on the O2 behind the Catalyst & move on with life.
I actually have a fouler plug laying around, is that a similar one? Or it needs to be an 18mm one? So use an antifouler and remove downstream sensor or add antifouler with the sensor? Appreciate your valuable help, as usual thumbsup
 
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Rock Auto has a California-legal converter for less than $200. You should also replace the oxygen sensors along with the cat. P0420 almost always means a bad cat (there are separate codes for oxygen sensors) Bank 1 and Bank 2 refer to cylinder banks, like you'd see in a V6. An inline engine like your I4 will only have one bank, so it is Bank 1 Sensor 1 means the one before the cat, or "upstream" Sensor 2 means the one after the cat, or "downstream"
 
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Thanks for the help, it's an I4 and autozone scan says P0420 - Bank 1 catalyst system efficiency was below threshold for a predetermined period of time. It means I should start with the upstream one first then or add an antifouler to downstream and call it a day? Thanks all.
 
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The downstream is the one that checks that the cat is working, the one that reports when the cat is not working, and the one that would cause the code to pop up.
 
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154k miles is way past the rated service life (typically 100k mi) of the heated 4/5-wire O2 sensors. So either the sensor is bad, or the sensor was allowed to be bad for so long that it actually damaged the cat. I'd start with a pair of O2 sensors, and if that fails to resolve the issue, then replace the cat. Unfortunately ECU's aren't too aggressive in detecting failed O2 sensors until well after damage has been done to chronic long-term increased fueling. If money's really tight, then just buy a downstream.
 
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Originally Posted by maverickfhs
Originally Posted by clinebarger
Don't bother with the O2 sensors.....The odds of having one emulate a faulty Catalyst is astronomical. Run a 18mm Antifouler on the O2 behind the Catalyst & move on with life.
I actually have a fouler plug laying around, is that a similar one? Or it needs to be an 18mm one? So use an antifouler and remove downstream sensor or add antifouler with the sensor? Appreciate your valuable help, as usual thumbsup
Your vehicle has 18mm O2 sensors...So the antifouler needs to match, You will most likely need the ream/drill it out to clear the O2. The objective is to the space the downstream away from the pipe/converter.
 
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Originally Posted by clinebarger
Don't bother with the O2 sensors.....The odds of having one emulate a faulty Catalyst is astronomical. Run a 18mm Antifouler on the O2 behind the Catalyst & move on with life.
I have done this so many times and it works everytime. Cheap $8 fix and 30 min of your time including drilling them out if needed. I double them up too.
 
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FL
Just had this same thing happen last month on my 2006 Acura TSX with the 2.4. In my mind, the best motor ever created by Honda. I had 238K when this code popped up. Cleared code, came back 50 miles later. Hooked up the Torque app and saw that the downstream O2 was switching very erratically. Changed that out. The erratic readings went away. I noticed my short-term trim readings were a bit high, so I changed out the upstream O2 to see if it would effect it. ST trim dropped by a few percentage points. The code has never came back. Car has never burned a drop of oil and is much, much more responsive since the O2 change out. Start simple. The two O2 sensors (Bosch and Walker) were about 150 total from Amazon. Easy change out. If it wasn't the sensors, I would have just cut the cat out and replaced with pipe.
 
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Originally Posted by Kozman011
Just had this same thing happen last month on my 2006 Acura TSX with the 2.4. In my mind, the best motor ever created by Honda. I had 238K when this code popped up. Cleared code, came back 50 miles later. Hooked up the Torque app and saw that the downstream O2 was switching very erratically. Changed that out. The erratic readings went away. I noticed my short-term trim readings were a bit high, so I changed out the upstream O2 to see if it would effect it. ST trim dropped by a few percentage points. The code has never came back. Car has never burned a drop of oil and is much, much more responsive since the O2 change out. Start simple. The two O2 sensors (Bosch and Walker) were about 150 total from Amazon. Easy change out. If it wasn't the sensors, I would have just cut the cat out and replaced with pipe.
I tend to agree with Kozman011 ... all good points. If you've never changed either up or downstream 02 .. .you're past due. I'd suggest using Denso sensors only on your Honda though... readily available on Amazon. And on the converter ... I just replaced the one on a 2004 Accord Sedan 2.4L with Walker #16299. Paid $140 or so on Amazon ... is a very good quality converter. Some of the cheaper ones only work for a month or so, and your P0420 code is back. Other than dealing with rusty bolts, was a direct fit. And that would definately be the time for a new downstream sensor, since it's in the middle of the converter. Other than the converter, you'll need front and rear gaskets, and a set of bolts from the hardware store .... 3 on front and 3 for rear. Good luck.
 
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