Check Engine Code - P0420
Check Engine Code - P0420
Ok, A couple of months back I had the flex pipe (had a hole in it) in the exhaust replaced. I paid almost $700 for the pipe (included new cats as well). Now I am getting a check engine light with code P0420 - I know it means a "lean" condition. Does this mean that I have a defective cat already? Or is the O2 sensor after the cat now defective and ****tin' the bed? The pipe was aftermarket and not a factory Toyota replacement (that would have cost $1200!!!) Any suggestions anyone has would be helpful? How do I check out the O2 sensor to see if it is the culprit? Anyone esle has this problem?
Thanks.......
Thanks.......
CL Community Team
Joined: Apr 2004
Posts: 17,329
Likes: 210
From: Miami, Florida
Can be your main cat or the sensor after it. Those are usually the two biggies.
However, you can also get gas leaking into the exhaust, causing high HCs, hydrocarbons and thus tossing this code.
At my altitude, combustion isn't a popular term with engines as it is at sea level. It is extremely important to have good, clean spark plugs. Another thing can be any tiny leak at any of the joints when your new exhaust was put in. I have them on my RX and I just need to put my hand by the joints and feel the heat. There is also a gasket in front of the main cat that can go bad and allow air to leak in.
However, you can also get gas leaking into the exhaust, causing high HCs, hydrocarbons and thus tossing this code.
At my altitude, combustion isn't a popular term with engines as it is at sea level. It is extremely important to have good, clean spark plugs. Another thing can be any tiny leak at any of the joints when your new exhaust was put in. I have them on my RX and I just need to put my hand by the joints and feel the heat. There is also a gasket in front of the main cat that can go bad and allow air to leak in.
Ok guys.....here's an update....I have checked all the flanges again that were touched when this aftermarket pipe was installed. I have NO LEAKS what so ever...I have check both A/F sensors in front of the CAT (both read 1.3 ohms - within spec) and have just checked the O2 sensor after the CAT (read 13.8 ohms - within spec). I have two more things to try - one is spark plug non-foulers to move the O2 sensor away a little more and the other is an O2 sim to fool the computer. I hope one of these works cause Ma. is the second stingiest state when it comes to emissions (other than Ca.) and I don't really want to pay another $500 for the Toyota OEM pipe (on top of the $700 I already paid for the after market pipe).
If anyone has other suggestions....I am all ears.
Thanks!
Chris
If anyone has other suggestions....I am all ears.
Thanks!
Chris
Driver School Candidate
Joined: Jul 2007
Posts: 16
Likes: 0
From: ga
go to www.nhtsa.dot.gov and check out the bulletins that Toyota has for your car. Maybe it involves this. I just found out the code I was getting had a recall on it and that when it comes on, it is usually nothing. See what they have to say.
Thanks for the advice......unfortunately there was nothing listed about this, only something to do with the steering wheel.
UPDATE: Installed 1 spark plug non-fouler to move the O2 sensor away from the exhaust stream (couldn't get a second one in there, not enough room). Reset the DTC & I/M and just need for the ECU to go through its diagnostics.....stay tuned....
Again, any additional input or feedback is welcomed.
Thanks!
UPDATE: Installed 1 spark plug non-fouler to move the O2 sensor away from the exhaust stream (couldn't get a second one in there, not enough room). Reset the DTC & I/M and just need for the ECU to go through its diagnostics.....stay tuned....
Again, any additional input or feedback is welcomed.
Thanks!
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man you jinxed me 
I looked up and today was the last day for my emissions and my check engine light came on last week or so. I would come on and sometimes it wouldnt. Well what do you know I failed the emissions and I got the P0420 code. I hope you find out what it is ivory98es3 that way I can get mine fixed
-Smitty
I looked up and today was the last day for my emissions and my check engine light came on last week or so. I would come on and sometimes it wouldnt. Well what do you know I failed the emissions and I got the P0420 code. I hope you find out what it is ivory98es3 that way I can get mine fixed -Smitty
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Smitty - didn't mean to "rain on your parade" 
but I hate the P0420 code to death!!
From what I have learned, the Lexus ECU is just very, VERY sensitive to any changes and it look like this aftermarket pipe I had put on is not up to Lexus' standards. I'd be interested when I get my emissions test what the readings will be (I refuse to pay out the @$$ for the OEM pipe = rediculous!!)
I'll keep everyone updated.
Peace......
but I hate the P0420 code to death!! From what I have learned, the Lexus ECU is just very, VERY sensitive to any changes and it look like this aftermarket pipe I had put on is not up to Lexus' standards. I'd be interested when I get my emissions test what the readings will be (I refuse to pay out the @$$ for the OEM pipe = rediculous!!)
I'll keep everyone updated.
Peace......
OK - here's another update fellas......
I have managed to fix this problem and eliminate the P0420 CEL and get my State Inspection sticker to boot
All it cost me was $9 for a O2 bypass.....soldered inline with the O2 sensor, drove my car for a bit, hooked up my OBDII scanner - low and behold, ALL systems and monitors were "READY".
Got my @$$ to the gas station - within 10 min. I had a brand new sticker
I have managed to fix this problem and eliminate the P0420 CEL and get my State Inspection sticker to boot
All it cost me was $9 for a O2 bypass.....soldered inline with the O2 sensor, drove my car for a bit, hooked up my OBDII scanner - low and behold, ALL systems and monitors were "READY".
Got my @$$ to the gas station - within 10 min. I had a brand new sticker
OK - here's another update fellas......
I have managed to fix this problem and eliminate the P0420 CEL and get my State Inspection sticker to boot
All it cost me was $9 for a O2 bypass.....soldered inline with the O2 sensor, drove my car for a bit, hooked up my OBDII scanner - low and behold, ALL systems and monitors were "READY".
Got my @$$ to the gas station - within 10 min. I had a brand new sticker
I have managed to fix this problem and eliminate the P0420 CEL and get my State Inspection sticker to boot
All it cost me was $9 for a O2 bypass.....soldered inline with the O2 sensor, drove my car for a bit, hooked up my OBDII scanner - low and behold, ALL systems and monitors were "READY".
Got my @$$ to the gas station - within 10 min. I had a brand new sticker
Now what exactly did you solder and where was the O2 sensor?-Smitty
Smitty -
I bought one of those O2 bypass similators off of Ebay - cost me $9 shipped.
I removed the driver's seat from the car and the O2 connector is right there under neath the carpet at the floor vents. I spliced into the blue wire on the sensor side with my bypass & voila! No more CEL!!
I bought one of those O2 bypass similators off of Ebay - cost me $9 shipped.
I removed the driver's seat from the car and the O2 connector is right there under neath the carpet at the floor vents. I spliced into the blue wire on the sensor side with my bypass & voila! No more CEL!!
Smitty -
I bought one of those O2 bypass similators off of Ebay - cost me $9 shipped.
I removed the driver's seat from the car and the O2 connector is right there under neath the carpet at the floor vents. I spliced into the blue wire on the sensor side with my bypass & voila! No more CEL!!
I bought one of those O2 bypass similators off of Ebay - cost me $9 shipped.
I removed the driver's seat from the car and the O2 connector is right there under neath the carpet at the floor vents. I spliced into the blue wire on the sensor side with my bypass & voila! No more CEL!!
Never done that but I'm up for a challenge. Besides would give me a chance to vaccum the palaces I cant get to normally. Thanks for the info. 
-Smitty
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