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P2A00 in 2006 Pathfinder after using "engine cleaner" fuel additive? Forums > > P2A00 in 2006 Pathfinder after using "engine cleaner" fuel additive? P2A00 in 2006 Pathfinder after using "engine cleaner" fuel additive?
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  #1  
Old 12-04-2016, 06:20 PM
afomenko afomenko is offline
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Default P2A00 in 2006 Pathfinder after using "engine cleaner" fuel additive?

I have 152K miles on the car, purchased at 151K.

It raised P0420 shortly after I bough it, so I frustratingly replaced upstream cat on passenger side and drove it for around 300 miles with no SES light, though this adventure is over.... not so fast!

Idling was a little bit rough, so replaced spark plugs, and noticed some carbon deposits on the base, so I decided to "clean it all" with "complete fuel system clean" type of fuel additive, and here is my reward: SES is on after 15 miles after I've put it into the tank :(

I can imagine this additive eats into carbon deposits on the top of pistons somehow, so likely it shifts A/F readings, not sure if it gets better once I get fresh gas into the tank?
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  #2  
Old 12-04-2016, 07:57 PM
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Only thing I can recommend is run the tank below 1/4 tank, fill the tank and erase the code and see if it returns.
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  #3  
Old 12-05-2016, 03:18 AM
afomenko afomenko is offline
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After further reading here, I will perform "Idle Air Volume Learning" and "Mixture Ratio Self-Learning", as it looks like my MPG is on the low side after I had battery disconnected for very long time when I worked on cat replacement.

Ordered vacuum hose to replace: not what they are very old, but seem to be stiff and may have some cracks I do not see.

Will post results here.
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Old 12-06-2016, 03:59 PM
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After running self-learning procedures and driving 200+ miles, so far no SES light, car runs smoother than before.

Did not get new gas in the tank yet.

So far getting around 16 MPG (city/highway mixed), while from prior owner I had an average of 18 MPG (looks like more on highway, based on CarFax).

Not sure if SES stays off, will post update in another week or so.
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Old 12-07-2016, 09:33 AM
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After re-calibration procedures MPG was around 17-18, then spiraled down to ~16 MPG and SES came up again after ~250 miles, same P2A00.

This time I checked each and every O2 sensor voltage in dynamics.

UPSTREAM:
B1S1 - almost constant at idle (0.26V), slowly drifts between 0.21V and 0.32V as I rev to 2000 rpm
B2S1 - drifts between 0.40V and 1.3V, jumps quite fast to revs of 2000 rpm

DOWNSTREAM:
B1S2 - short-cycles between 0.10V and 0.85V
B2S2 - long-cycles between 0.10V and 0.77V

The cat I replaced before is on Bank 1 due to P0420.

I do not know the car history, but Bank 1 cat was rusting out its heat-shields (coming out in pieces), very rusty overall, while Bank 2 cat was shiny and glossy, had new bolts (slightly rusted), had upstream (B2S1) sensor connector broken form the clamp (likely somebody was trying to yank it out, not to remove it carefully) and was looking like it is there for much less than 10 years.
Bank 2 cat looked to be an original Nissan, not any type of aftermarket, CarFax shows owner maintained car on the nearby dealership.
Downstream O2 sensors seem to be both from original factory batch, not much difference in visual appearance.

I assumed that car was sold because previous owner was scared from some 4-digit bill after replacing one cat and sensor and got rid of it.

Now, given this history, does it look like B1S1 is due for replacement?
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Old 12-10-2016, 03:14 PM
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Replaced upstream sensor in Bank 1, performed A/F relearning.

Checking dynamic voltage: it will stay around 0.30V at idle (why?!?)

At first I suspected sensor is at fault, but then I run with breaking by engine (artificially creating rich condition): it jumps up to 0.90V, so it is good.

On Bank 2, I have steady 0.60V at idle, 0.1..0.95V for the full range under the same engine-breaking test.

For some reason, ECU decides to feed Bank 1 lean, and Bank 2 slightly rich.

Any ideas?
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  #7  
Old 12-10-2016, 07:14 PM
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The rear sensors are oxygen sensors, but, the front sensors are air/fuel ratio sensors. They operate a little differently. Air/fuel ration sensors are difficult to monitor by simply viewing the voltage output. One of the things I do remember is that if you have this code and replace the sensor, you need to erase the self-learning memory when you erase the stored code, as well. If not, the code re-triggers for whatever reason. If you do that and it still triggers, I would follow the diagnostic steps in the factory service manual for the P2A00 code. There should be and "Engine Control" section of the 2006 Pathfinder factory service manual in the "knowledge base" at this site, available for download. This info may also be helpful:

P2A00 2006 NISSAN PATHFINDER Air Fuel Ratio Sensor Circuit Range/Performance Bank 1 Sensor 1

You may also want to check for any applicable technical service bulletins while your in the "knowledge base."
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Old 01-07-2017, 07:35 PM
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if anybody cares where it went

voltage reported via OBD2 proved to be a red herring, as some normally running vehicles with no codes reported have exactly same values reported

I've completely eliminated all and any things in intake side: plugges small leak in intake manifold on gaskets, cleaned injectors, swapped ignition coils between banks and jonjectors between banks - it all made car to run smoother, but P2A00 was reappearing after some time

finally, I found leaks in catalyst I've placed when dealing with P0420, it made me think I'm on right track, then removing catalyst, I found that welding on the flange to downstream catalyst leaked substantially, broke off as I was removing catalyst

no mystery anymore, replacing both catalysts on passenger side and likely this is the end of story

what was happening:
- leak between catalysts was introducing oxygen visible to downstream O2 sensor, but not to upstream A/F sensor
- ECU was trying to add fuel (indeed I observed black soot on this side, not on another)
- downstream O2 sensor would continue to see oxygen
- eventually ECU would condemn A/F sensor and throw P2A00
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