# 03 Altima P0420, P1456 & P0442 HELP!



## iFreeStylinq (Feb 25, 2015)

My SES light came on about a week ago and i hook up my ODB2 scanner and get all those codes in the same order. I know i probably need to change the catalyst converter (P0420) and the other two code both seems to point out a leak in the EVAP system. I both a new gas cap and that didnt solve the problem. Can the P0420 also caused the other two codes? or the other way around.


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## rhsquicksilver (Mar 9, 2015)

*03 Altima P0420, P1456 &amp; P0442 HELP!*



iFreeStylinq said:


> My SES light came on about a week ago and i hook up my ODB2 scanner and get all those codes in the same order. I know i probably need to change the catalyst converter (P0420) and the other two code both seems to point out a leak in the EVAP system. I both a new gas cap and that didnt solve the problem. Can the P0420 also caused the other two codes? or the other way around.



This might not help at all, and I'll defer to someone with actual mechanical background (I'm in anesthesia...)
P0420 usually refers to A) the cat wearing out like you said, and/or B) the downstream O2 sensor sending bad data, obviously on account of a bad cat or the sensor element going out. ~75% of cases I've read about are due to the sensor. This is a MUCH cheaper part to replace, because if you replace a converter and still have a bad sensor, it will still send bad data to the ECM. 
You can find sensors as low as $20 for a new, open box piece. I'd start there. For the other two codes, that's where I'll bow out!

EDIT: this is based on my experience with Hondas... Sorry if that completely discounts my attempt to help!


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## iFreeStylinq (Feb 25, 2015)

rhsquicksilver said:


> This might not help at all, and I'll defer to someone with actual mechanical background (I'm in anesthesia...)
> P0420 usually refers to A) the cat wearing out like you said, and/or B) the downstream O2 sensor sending bad data, obviously on account of a bad cat or the sensor element going out. ~75% of cases I've read about are due to the sensor. This is a MUCH cheaper part to replace, because if you replace a converter and still have a bad sensor, it will still send bad data to the ECM.
> You can find sensors as low as $20 for a new, open box piece. I'd start there. For the other two codes, that's where I'll bow out!
> 
> EDIT: this is based on my experience with Hondas... Sorry if that completely discounts my attempt to help!


Thanks i'll have it checked out before i by a new cat.


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## smj999smj (Jan 1, 2006)

The P0420 code is likely due to an inefficient catalytic converter. If you have an engine that you need to add oil to on a regular basis, then you likely have a bigger issue of bad rings and it will ruin the new converter. If not, you should be able to get away with just the converter. Usually if there is an oxygen sensor issue, there will be a trouble code for it. If you decide to replace the sensors first, I would stick to NTK brand, which is the OE sensor, and you can get them for a fair price at Rockauto.com. The reason I ask about the oil is that it was common on the early L31's with the QR25DE to burn oil. The EGR system uses the variable valve timing to crack open the exhaust during the intake stroke to suck in exhaust gas for EGR rather than a conventional EGR valve system. The problem was there were issues with the upstream catalytic converter breaking down due to an issue with the ECM programming. The bits of catalyst media would bet sucked into the combustion chamber, scoring the walls, and create an oil burning engine. Nissan had a campaign to address the issue, including an ECM update and some heat shields, and in some cases replacement of the engine short block and catalytic converter/exhaust manifold assy. 

As far as the Evap codes, often the problem is a sticking vent control valve, which is attached to the evap canister at the left, rear of the vehicle. The valve is normally open to vent the system, but is commanded closed by the ECM when it tests the evap system for leaks. If the valve sticks closed, it will make it difficult to fill the tank with gas. If it sticks open, it will cause a leak code. I linked to a web page with some pics and more info on it. Of course, there are other things that can cause this code, but this is the most common. The only way to be sure is to follow the diagnostic procedures for the codes using equipment, tools and a factory service manual. Just throwing parts on to fix a problem is always a gamble.

http://www.justanswer.com/nissan/20b0c-getting-odb2-error-p1456-minor-evap-common-issues.html


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## iFreeStylinq (Feb 25, 2015)

smj999smj said:


> The P0420 code is likely due to an inefficient catalytic converter. If you have an engine that you need to add oil to on a regular basis, then you likely have a bigger issue of bad rings and it will ruin the new converter. If not, you should be able to get away with just the converter. Usually if there is an oxygen sensor issue, there will be a trouble code for it. If you decide to replace the sensors first, I would stick to NTK brand, which is the OE sensor, and you can get them for a fair price at Rockauto.com. The reason I ask about the oil is that it was common on the early L31's with the QR25DE to burn oil. The EGR system uses the variable valve timing to crack open the exhaust during the intake stroke to suck in exhaust gas for EGR rather than a conventional EGR valve system. The problem was there were issues with the upstream catalytic converter breaking down due to an issue with the ECM programming. The bits of catalyst media would bet sucked into the combustion chamber, scoring the walls, and create an oil burning engine. Nissan had a campaign to address the issue, including an ECM update and some heat shields, and in some cases replacement of the engine short block and catalytic converter/exhaust manifold assy.
> 
> As far as the Evap codes, often the problem is a sticking vent control valve, which is attached to the evap canister at the left, rear of the vehicle. The valve is normally open to vent the system, but is commanded closed by the ECM when it tests the evap system for leaks. If the valve sticks closed, it will make it difficult to fill the tank with gas. If it sticks open, it will cause a leak code. I linked to a web page with some pics and more info on it. Of course, there are other things that can cause this code, but this is the most common. The only way to be sure is to follow the diagnostic procedures for the codes using equipment, tools and a factory service manual. Just throwing parts on to fix a problem is always a gamble.
> 
> http://www.justanswer.com/nissan/20b0c-getting-odb2-error-p1456-minor-evap-common-issues.html


I recently purchase this vehicle so i don't know if it burns oil or not. The last oil change (judging from the sticker) was in august, and i'm going to do an oil change this weekend.

I can get the catalytic converter with the O2 sensors for $250 so i might just change them both at the same time. Thinking about doing this my self instead of paying another $150 for labor which in turn can get me the vent control valve. Thanks for all your help, at least now i know where to start!


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