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00 Sentra 1.8 New OEM MAF now P0420 code Forums > > 00 Sentra 1.8 New OEM MAF now P0420 code 00 Sentra 1.8 New OEM MAF now P0420 code
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  #1  
Old 08-18-2012, 09:25 AM
ragmalibu ragmalibu is offline
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Default 00 Sentra 1.8 New OEM MAF now P0420 code

Hi:
I have done a lot of research and still nothing close to what I had going on with my car. I have been having the notorious P0171 (lean bank 1) code and was using MasterTech tool to diagnose, read the O2 front and rear switching speeds and I came to conclusion that it was the MAF. I had tried to clean it and it didn't work but car continued to hesitate and not rev up well. O2s switched, maybe not at the rate I wanted to see, but they looked decent (5 times in 10 seconds for the front, and slower for the rear). I bought an OEM MAF and air filter at the dealer and now the car runs great, no hesitation, but after one drive, I am now getting the P0420 code (Cat efficiency bank 1). My O2s are not switching like before, the front one is pretty flat and that is what worries me. If the front was good and the rear switched at the same rate, then I would agree with the CAT being bad but now, after the new MAF, the O2s don't respond like with they should.
PLease give me some guidance..
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  #2  
Old 08-18-2012, 12:00 PM
JudoJohn JudoJohn is offline
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p0420 is not a MAF code. it is something to do with the O2 sensors and or the cat.
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  #3  
Old 08-18-2012, 01:52 PM
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bennyb53 bennyb53 is offline
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agree with JudoJohn. replace your post-cat O2 sensor. idk how many miles your car has. i also recommend to replace the pre-cat O2 sensor. i had my P0171 dtc just before turning 96k miles which is in the upper limit. went ahead to replace S1 since the two works in tandem. Bosch or NGK are your choices.
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  #4  
Old 08-18-2012, 09:52 PM
ragmalibu ragmalibu is offline
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Quote:
Originally Posted by bennyb53 View Post
agree with JudoJohn. replace your post-cat O2 sensor. idk how many miles your car has. i also recommend to replace the pre-cat O2 sensor. i had my P0171 dtc just before turning 96k miles which is in the upper limit. went ahead to replace S1 since the two works in tandem. Bosch or NGK are your choices.
Yes, I know the P0420 is not a MAF code, but what I am saying is that with the old MAF, I get the P0171 lean code, and with the new MAF, I get the P0420 catalytic efficiency failure. I've swapped them back and forth and with the old MAF, I get the 02s switching but the car runs lean. When I install the new OEM MAF, I get the P0420 Cat code since the O2s don't really switch right. The car has 115K miles and I know the 02s are due but they seem to switch well with the old MAF.
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  #5  
Old 08-19-2012, 01:09 AM
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bennyb53 bennyb53 is offline
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try do the Air//Fuel Mixture Self-Learning procedures found in the DIY section. btw - P0171 code is O2 sensor 1 or pre-cat. Aging sensors are still functioning but slow in switching response.
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  #6  
Old 08-19-2012, 10:18 AM
ritter ritter is offline
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You can save . save . AND save by replacing your O2 ,As much as 30 percet!
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  #7  
Old 08-19-2012, 02:30 PM
ragmalibu ragmalibu is offline
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Yes, thank you. I've done the learning procedure. I will do the 02 sensors since they are old.
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  #8  
Old 08-21-2012, 12:12 PM
ragmalibu ragmalibu is offline
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Looking at the o2 sensors I see them switching almost equally but the downstream swings a little less. I am confused as to why the second sensor needs to be changed. The test is looking for a percentage less swing on the secondary one, and that is why an extension is usually used to trick the ECM reading and make is less pronounced in voltage. My sensor upstream sensor is swinging at a decent rate but not .2 to .8 but it swing from 0 to around .6 so it peaks out at a lesser voltage than expected. Why is the recommendation on many sites to replace the second sensor? If I replace the first sensor and it gives more peak to peak reading and the secondary one swings at a lesser peak to peak, wouldn't that make this the proper cure? Please let me know your thoughts, Im about to order some o2 sensors but I'd like to know what you guys/ladies feel.. Also, i found some good prices at RockAuto.com, are aftermarket sensors ok to use. I know MAFs are recommended OEM, but what experiences have you had with aftermarket o2 sensors.

thanks again
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  #9  
Old 09-12-2012, 11:57 AM
ragmalibu ragmalibu is offline
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Ok, for those with 2000 sentra, california car, with under 150,000 miles. I have been battleing with the p0420 code and had tried everything here and the problem still showed it was the CAT not the sensors. I had read somewhere that there was an extended warranty, but I didn't think it applied to mine just the newer sentras so I hadn't pursued it. I finally called the dealer and my car, based on the car being less than 150,000 miles, and a california car, it was fully replaced and covered by Nissan. Others may have already posted this but I could not find it.

Good luck. By the way, if you don't need to pass smog and just need to get rid of the p0420 code and don't want to change to a header, add a 500K ohm resitor accross (that means cut the wire, add a resistor across) the Black wire on the read O2 sensor of the bank that is failing (in this case Bank 1) and the code will go away. It will not pass smog, but it will get rid of the code for those non smog states.

Good luck.
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