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2003 Sentra SE-R with engine code P0420 Forums > > 2003 Sentra SE-R with engine code P0420 2003 Sentra SE-R with engine code P0420
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  #1  
Old 12-28-2009, 07:13 AM
mike_s mike_s is offline
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Default 2003 Sentra SE-R with engine code P0420

I recently had my check engine light come on in my 03 Sentra SE-R. I pulled the code and it came up with: P-0420 "Catalyst Efficiency Below Threshold (Bank 1)".

Contacted the dealer and was advised to come in and spend $100 to diagnose and then some more to repair what ever is wrong. Is this a common code and does anyone have suggestion on what may be causing?

Thanks
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  #2  
Old 12-29-2009, 08:23 PM
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It is common on some Nissan models, but not in your model year. Here is a list of all the model affected by that code: Search - Nissanhelp.com

In some model you have to reprogram the Engine Control Module (ECM), but in other model catalytic converter needs to be replaced to repair the problem. I suggest reprogramming the ECM first. Unfortunately only the dealer may be able to do that for you.
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  #3  
Old 12-30-2009, 05:55 AM
mike_s mike_s is offline
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Thanks for the reply and info! I cleared the code after checking it and the check engine light has not yet returned. Is there any reason I should not continue to drive as normal as long as it stays off? Any potential for damage?

Thanks
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  #4  
Old 01-04-2010, 11:38 AM
mike_s mike_s is offline
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I wanted to follow up for anyone else that may be unaware of numerous reports of pre-cat failures on Nissan models with the QR25DE engine. While I'm not certain that this is the reason for my P0420 code, I am sufficeintly concerned about this being a potential problem and have ordered an new header with out the cat. My Sentra SE-R has a second cat down stream and from everything I've read, removal of the pre-cat will not be a problem for emmission testing.

The problem with the design of the QR25DE engine is that the screen keeping the catalytic material in place located in the exhaust manifold (just a few inches away from the motor) has a tendancy to break down. This is caused by excessive heat due to it's proximity to the motor. When this screen breaks down, the catalytic material is "sucked" back into the motor. The material enters the cylinders and causes scoring on the cylinder walls. This scoring can and often does lead to excessive oil consumption and catastrophic engine failure. It appears that there are some not well advertised recalls out there to fix this problem (ECM reprogram and exhaust header replacement) but all of the research I've done leads me to believe that replacing the header with a cat-less model is the best solution. My car has 118k miles and has passed the 8yr/80k warranty that would allow me to have this issue serviced under the recall.

I will take a look at what kind of shape my pre-cat is in when I complete the header replacement and report my findings for anyone interested.
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  #5  
Old 01-04-2010, 05:24 PM
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mpe235 mpe235 is offline
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Quote:
Originally Posted by mike_s View Post
I wanted to follow up for anyone else that may be unaware of numerous reports of pre-cat failures on Nissan models with the QR25DE engine. While I'm not certain that this is the reason for my P0420 code, I am sufficeintly concerned about this being a potential problem and have ordered an new header with out the cat. My Sentra SE-R has a second cat down stream and from everything I've read, removal of the pre-cat will not be a problem for emmission testing.
.
Removal of that cat. will definately be a problem for emissions testing. You will have a constant check engine light with a P0420 code due to the missing cat.
The rear oxygen sensor is mounted behind that converter. The second cat you see down stream is not monitored by the cars computer.
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  #6  
Old 01-05-2010, 03:59 AM
mike_s mike_s is offline
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Thanks for the response. Yes it will continue to trip the CEL if you just re-install the O2 sensors in the same stream. I've found a couple of solutions to avoid this problem. One is to use a spacer that will hold the sensor out of the exhaust stream enough to provide a different reading from the 1st. The other option is to relocate the second O2 sensor down stream of the remaining cat and that too should alleviate the problem. I should have the change out completed soon and will post the results including any CEL issues.
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  #7  
Old 03-01-2010, 04:42 AM
mike_s mike_s is offline
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Default Repair Completed

I wanted to take a minute to post a follow up to my cat/header issue. Last week I removed the stock exhaust manifold and installed a cat-less header. The install went smooth (took about 3 hours) and has been running well ever since. When I tapped the OEM exhaust header there was some material that came out of the top end. It wasn't huge chunks, but I no longer have to worry about the cat being ingested by the motor. I used the CEL fix supplied by the manufacturer and have had no CEL issues. There is a bit more noise under hard acceleration, but no noticeable noise difference when cruising at 75mph. It is however much more responsive over 2500 RPM and the extra 14hp are noticeable. I would strongly recommend this fix to anyone concerned about the pre-cat failure issue with the 2.5L motor. Parts - $287 Install - 3 hours (at home without hoist)
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  #8  
Old 03-01-2010, 07:13 AM
b1ynd
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I did the same with my car just after i bought it its a 2005 SER spec V the only thing is my o2 sensors keep going on (the header one) how did you solved this issue? I have a DC sports header
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  #9  
Old 03-01-2010, 08:08 AM
mike_s mike_s is offline
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i bought a megan racing header and asked them to include their CEL fix. It is a short extension that threads into the header for the lower O2 sensor. You then thread the O2 sensor into it. It pulls the sensor out of the exhaust stream enough that you get 2 different readings from the upper and lower sensors and therefore no CEL. You can easily find one by going to them or google CEL fix.
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  #10  
Old 03-01-2010, 10:21 AM
b1ynd
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ty a lot :p one question though if i install the cel does the readouts that the o2 sensor takes now are acurate enough to know if my engine is running lean or reach?

Last edited by b1ynd; 03-01-2010 at 10:26 AM.
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  #11  
Old 03-01-2010, 11:15 AM
mike_s mike_s is offline
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Everything I've read indicates to me that the secondary O2 sensor was really only used to monitor the health of the pre-cat. I didn't see anything that warned of that being a problem and in the few hundred miles I've driven since the installation have seen no problems.
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  #12  
Old 04-27-2017, 06:34 AM
Bookmdano Bookmdano is offline
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Hi,
I am not sure if this is the correct tread for this issue or not. I have a 2004 Spec -V with the Pre-cat removed. I am not familiar with a CEL fix. I was told that the computer should be "re-flashed" to get the light to turn off. I have emissions due soon and wasn't sure what to do. Thanks for any advice.
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