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I need smart people help with my CEL P0420

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Old 11-03-2011, 10:25 AM
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Originally Posted by GD916
YES! not that it matters, but its usually referred to as "a/f" ratio.
Wait so 'yes' something bad will happen. OR Yes the first 02 sensor controls the A\F ratio?
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Old 11-03-2011, 11:27 AM
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0420? I thought it was pretty obvious that your car wanted to get high.
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Old 11-03-2011, 11:34 AM
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Originally Posted by brucelee
0420? I thought it was pretty obvious that your car wanted to get high.
Why you no serious?
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Old 11-03-2011, 11:48 AM
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I would replace the rear O2 sensor first as its relatively cheap. If that doesn't work it's the cat.

-- Ed
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Old 11-03-2011, 12:11 PM
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Originally Posted by brucelee
0420? I thought it was pretty obvious that your car wanted to get high.
Haha when my friend got the call from the dealership to tell him what the cel code was, we happened to be smokin and it cracked us up really hard when he said " your car has a 420 code"
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Old 11-03-2011, 12:15 PM
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Originally Posted by EQ Tuning
I would replace the rear O2 sensor first as its relatively cheap. If that doesn't work it's the cat.

-- Ed
That's what I figured. Alright I'll grab one, along with a cabin filter to replace my 10yo old one. lol
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Old 11-03-2011, 01:20 PM
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My car still has this CEL.. lolz.

Even replaced all o2 sensors and Cat. No biggie, still gets good mileage and a little scamming the smog place by pulling the battery and driving it easy for a week or so get me to pass. Only annoying thing is the light itself.
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Old 11-03-2011, 01:36 PM
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Originally Posted by smokey25
My car still has this CEL.. lolz.

Even replaced all o2 sensors and Cat. No biggie, still gets good mileage and a little scamming the smog place by pulling the battery and driving it easy for a week or so get me to pass. Only annoying thing is the light itself.
Really your car STILL has this? After those many years? Just to make it clear, your exhaust system (header back) is all completely stock? It is a very common cel code for our imprezas. Im running catless right now with EL headers and custom cat back. No essence of emission cels what so ever. Never got a 420 code since I made the changes. I can let you know of a very affordable mod that might fix this issue for you.
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Old 11-03-2011, 01:43 PM
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Originally Posted by pho_shizzle
Really your car STILL has this? After those many years? Just to make it clear, your exhaust system (header back) is all completely stock? It is a very common cel code for our imprezas. Im running catless right now with EL headers and custom cat back. No essence of emission cels what so ever. Never got a 420 code since I made the changes. I can let you know of a very affordable mod that might fix this issue for you.
I'd like to hear of that 'mod'...
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Old 11-03-2011, 01:48 PM
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Originally Posted by EQ Tuning
I would replace the rear O2 sensor first as its relatively cheap. If that doesn't work it's the cat.

-- Ed
Do you, or anyone else, happen to know the part number for the rear O2 sensor?

-Brian
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Old 11-03-2011, 01:55 PM
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Originally Posted by pho_shizzle
Really your car STILL has this? After those many years? Just to make it clear, your exhaust system (header back) is all completely stock? It is a very common cel code for our imprezas. Im running catless right now with EL headers and custom cat back. No essence of emission cels what so ever. Never got a 420 code since I made the changes. I can let you know of a very affordable mod that might fix this issue for you.
Hahaha I know right. It is all stock exhaust parts. I had the cat replaced and the code did go away for maybe 2 months, and came back. I then replaced the 02 sensors and they did nothing. I am beginning to suspect there is an exhaust leak in the header from when the crack was welded. The reason i suspect it is cuz when I have seafoamed the car some white smoke comes up from the underside of the engine.. I'm guessing there is a leak.

It just hasnt been much a problem besides the light for me to really care

I know there are sensor "extenders" which place the sensor farther from the exhaust gas which can get rid of the code.. problem is up here (I live in Vancouver, BC) AirCare (smog check) definitely give the underside the mirror treatment looking for it.

Funny thing is.. everytime the report comes out it says "Catalaytic system not ready" because I pull the battery about a week before the test to clear the CEL.. and they let me pass with that one system in not ready status
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Old 11-03-2011, 02:14 PM
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^ Yea I was going to recommend a specific type of extender, but if your AirCare really does visually inspect everything, then you are cornered and limited to alternatives. Sorry to hear that! Well then I guess its just one of those bad egg problems in a batch. As long as you are passing with your method lol.
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Old 11-03-2011, 03:00 PM
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Originally Posted by pho_shizzle
^ Yea I was going to recommend a specific type of extender, but if your AirCare really does visually inspect everything, then you are cornered and limited to alternatives. Sorry to hear that! Well then I guess its just one of those bad egg problems in a batch. As long as you are passing with your method lol.
Would you mind sharing that info with those of us with the same problem?

-Brian
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Old 11-03-2011, 05:23 PM
  #29  
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Originally Posted by Hoofus
Is a cat really required in our cars, or does the first 02 sensor control the F\A ratio.
IE: Will anything bad happen if I run without a cat?
well, you will be illegally polluting the air, and if you happen to get caught the fines are pretty substantial, but if you don't get caught...
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Old 11-04-2011, 09:09 AM
  #30  
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Originally Posted by psoper
well, you will be illegally polluting the air, and if you happen to get caught the fines are pretty substantial, but if you don't get caught...
No emissions where I live.
In any case, I have a stripped head stud hole? on my header on the passenger side, that could be causing a leak and why its throwing the error. Perhaps it would behoove me to have a shop tap the hole a bit bigger and place a larger bolt in there....
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