# Nissan Pathfinder - P1283 & P0420



## Bilbo007 (May 31, 2015)

Hi,

I have a Nissan Pathfinder 2006 R51 V6 Petrol. The engine light keeps coming on with *P1283* (Air Fuel Ratio Sensor 1 Lean Shift Monitoring Bank 2) & *P0420* (Catalyst System Efficiency Below Threshold (Bank 1) codes.

I have just replaced the rear catalytic converters on both banks and the mechanic told me the front converters looked clear. Based on this article the front catalytic converters could be causing the problem: http://www.justanswer.com/nissan/4y...oad-05-nissan-xterra-p1283-rob.html#re.v/181/. I also brought CRC MAF cleaner today and cleaned the MAF sensor as that was one of the fix recommendations. Didn't make any difference. 

On a side note and not sure if its related, after driving the car I can smell fuel when standing close to the filler cap. Its quite strong and when releasing filler cap there is a big hiss and you can hear what sounds like the fuel take shrinking as it may have been expanded (Assumption). Could this sort if thing be causing high fuel pressure which is one of the things to check for with the P1283 and P0420 codes? 

Does anyone have any suggestions as to what else might be causing the issue? I'm not convinced its the front cat converter since I just had it checked and they said it was clear.

Thanks


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## smj999smj (Jan 1, 2006)

Okay, well the air/fuel ratio sensor is essentially the oxygen sensor (there are some subtle differences). Bank 2/Sensor 1 is the front (or upstream) sensor on the left side of the vehicle. This would be NTK oxygen sensor P/N: 24320 (NTK is the OE supplier of the sensors to Nissan). Any time you get a catalyst code with another engine management code (i.e. oxygen sensor, mass air sensor, ignition or misfire codes, etc.), you should address the engine management code, erase all codes, and then wait and see if the catalyst code re-occurs. Also, the front, or upstream, catalytic converters, are the only one monitored by the ECM, as they sit between the upstream and downstream oxygen sensors. The rear converters rarely fail as the upstream converters act like a filter before the exhaust gets to the rear converters. You can remove the rear converters completely and it will not trigger a trouble code in the ECM. So, unless they were leaking or rattling inside, you wasted money by replacing the rear converters. Chances are you only needed to replace the left, front oxygen (or "air/fuel ratio") sensor.


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## Bilbo007 (May 31, 2015)

Thanks for the info, very helpful.


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## Bilbo007 (May 31, 2015)

I've been looking at the air/fuel sensor voltages and I'm getting similar readings to the user at the link below. He apparently fixed his by replacing O2B1S1. Basically O2B1S1 sits at between .285 - .315 volts on the OBD reader. All other sensors fluctuate a lot more (Primarily O2B2S1) which was the suspected faulty sensor based on P1283 code.

Could it be O2B1S1 which is faulty with codes P1283 and P0420? Would you recommend replacing sensor 1 for both bank 1 and 2? 

The Nissan Path :: View topic - OBD Code P1271 Air Fuel Ratio

Thanks for your help.


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## smj999smj (Jan 1, 2006)

P1283 is bank 2/sensor 1 air/fuel sensor. P1271 is the bank 1/sensor 1 air/fuel sensor. I would recommend replacing the sensor for your given code, which is the left side, front sensor. If you feel like replacing both sensors at the same time, that's entirely up to you.


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## Bilbo007 (May 31, 2015)

Thanks again. I've ordered sensors for both banks 1 & 2. Will post again if it fixes the issue.


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## Bilbo007 (May 31, 2015)

I have replaced O2S1B1 and O2S1B2. Codes P0420 and P1283 have cleared. 

Now P0430 is the only code coming up. Looking at the voltages of the O2 sensors O2B1S1 fluctuates between .285 and .315v (same as before replacement) even although it's just been replaced. 

Would you agree this is worth looking into for the P0430 code? Is there a chance the car isn't alerting me of the bad O2 sensor reading E.g P1283? What else can I check if the sensor has been replaced and still not getting correct O2 sensor readings?

Thanks,


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## airsmith (Aug 21, 2015)

I am experiencing the same thing on a V6 2005 Nissan Frontier. Already replaced all 4 O2 sensors, both upstream Cats and am getting a P1283 and P0420. I can't find the problem. Assuming now it may be an injector but am not throwing an injector code. Have looked for vacuum leaks and can't find any. Already replaced MAF sensor and PCV valve.
I've taken it to a local Nissan dealer and a general mechanic and still haven't fixed the problem. Just keep replacing parts and throwing the same codes.

Has anyone else had this problem? I would like to finally get this fixed. Extremely frustrated......


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## Bilbo007 (May 31, 2015)

Hi Airsmith, replacing O2B2S1 cleared my 1283 and 0420 codes. The replacement O2B1S1 may be faulty so I'm waiting for a replacement. 

One think to check is that your fault history has been cleared. Even if you fix the issue by replacing sensors, the engine light will re-appear until history has been cleared. This can be done with an OBD2 reader or disconnect the battery for 1hr. 

Do you have a OBD2 meter? If so can you measure the approximate voltages of the four pre/post cat sensors? They should fluctuate between .5 and 1volt when running. I'm replacing O2B1S1 because it's stuck between .285 and .315v. 

Please respond to this forum with your findings as I may have a similar issue to you. 

Thanks,


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## smj999smj (Jan 1, 2006)

Air/fuel ratio sensors, like those that are often used for late model, pre-cat sensors, operate much differently than the oxygen sensors which are used post-cat on most late model cars, so testing them isn't the same. If you want a tutorial on the different types of exhaust gas sensors, you might be interested in this article:

https://www.discountconverter.com/c...ws_page.cfm?Key=catalytic_converter-&News=248


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## Bilbo007 (May 31, 2015)

Thanks for the link, very informative. The article states that OBD11 doesnt give an accurate voltage reading and to consult the workshop manual for testing methods. I'll take a look at the manual tonight.

Thanks


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## Bilbo007 (May 31, 2015)

Ok after the issues described above, the final code coming up in P0430. I'm keen to get your opinion on how to troubleshoot from here:

When I first bought the vehicle I put ethanol fuel in it which it hated. I got multiple cylinder misfires and had to replace O2B2S1 which cleared my 1283 and 0420 codes. I have since replaced O2B1S1 twice and it hasn't cleared P0430. When clearing the P0430 code it takes approximately one week of driving before the engine light comes back on. I don't know if its just me but when the engine light comes on it feels like the vehicle runs more roughly.

From here I'm considering the following steps:
- Confirm O2B1S2 is working correctly
- Confirm O2B1S1 is definitely operating correctly (Need to check workshop manual as mentioned in a previous post)
- The mechanic has already checked the pre-cat and replaced the post cat however keen to get the pre-cat checked again just in case
- Replace coil packs and plugs

Have I missed anything? Are there any other things I should be checking? Any suggestions would be appreciated.

Thanks,


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## Boardingbo (Aug 22, 2016)

Hello, I too have had the same set of codes (P1283 and P0420). After reviewing this thread and many others, I went ahead and replaced the O2, Bank 2, Sensor 1 in hopes to clear out the P1283. After completing the job and clearing the codes, and relearning the system, I am still getting both these errors. Also, I got the additional P0430. At this point, I am assuming both Cats are bad. If I replace both Cats, will that also eliminate the P1283 or is there something else to address the P1283 first?


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## Pootypank (Feb 6, 2019)

Has anyone tried replacing the plastic intake manifold? Maybe that is the source of the burnt out catalytic converters? Seems like too much air gets sucked it. Seems like once it gets to operating temp. It starts acting up. I replaced the camshaft position sensor after getting that code ( I think p0340 or 345) which was causing a complete zeroing out on the gauges at times and then eventually stalling and becoming harder to start the longer I waited to swap it (pain in the rear btw) I think the other codes are due to a vacuum leak and I will start by replacing the plastic intake plenum with 124000 miles on it. If that doesn't help with the issue, I will try to find other possible leak sites maybe in the throttle body area, hopefully a new gasket would help when I replace the intake, but maybe it gets caught open or something leading to the lean condition which in turn burns out the cats. You put new ones in, burn them out way sooner than fixing the gas or air issue and then getting new cats. With just throwing sensors at it, you just waste money and the codes come back after the vehicle completes all the monitors and these fail again, I am hoping to solve the cause of the issue, then fix the destruction it caused to the rest of the three way catalyst system. Wish I could get my hands on a consult-II to rent though and verify everything and see the data after running the appropriate tests. It is nice that you can find the pdfs to all of the sections of the repair manual online for free. Super helpful. As is YouTube with awesome material to help get many common issues fixed. I will try to update after replacing the air intake manifold.


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## smj999smj (Jan 1, 2006)

I haven't heard of any issues with the resin upper plenums, so far. A lot of the catalytic converter failure do occur after cam position failures in which misfiring can cause raw fuel to be sent through the converter. Another issue I've heard of is O2 sensor codes being caused by cracks in the exhaust manifold at the flanges where they bolt to the upstream converter, as well as on the converter, itself.


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