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I got an 04 Nissan Sentra and I got a (P1273 Nissan – Air Fuel Ratio Sensor 1 Lean Shift Monitoring Bank 1) code that popped up on it. Looking to see what the probable cause for this code to pop up? Is this a rare code that popped up on this car? There’s no noticeable symptoms going on with the car. Would I be able to test the possible problems with a Obd2 scan tool with live data or some other how? Because I have read it could be 02 sensor, MAF sensor and have heard that you can get reads for that off an obd2 scan tool with live data?
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Your front o2 is telling you your lean to much oxygen. which can be cause by vacuum leaks,fuel pressure,
dirty maf. bad or dirty injectors. seeing your not noticing drive ability issues. Clean the maf and connector
with the appropriate cleaner. next clean the front o2 connections. more in this link.http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Also forgot to mention the car has a small exhaust leak on the flex pipe under the car, But was told by 1 person the code is not on because of that. I did clear the code and the engine light came back on in 7 miles. But can certain things be checked threw an obd2 live data to rule things out liike 02 and maf sensors? college man you said the o2 sensor is telling me there’s a problem with something, could it be the 02 need to be changed out because it’s bad?
[quote=”jspe8437″ post=141822]Also forgot to mention the car has a small exhaust leak on the flex pipe under the car, But was told by 1 person the code is not on because of that. I did clear the code and the engine light came back on in 7 miles. But can certain things be checked threw an obd2 live data to rule things out liike 02 and maf sensors? college man you said the o2 sensor is telling me there’s a problem with something, could it be the 02 need to be changed out because it’s bad?[/quote]
The o2 is reading a lean condition. Either the sensor is correct or it could be stuck lean
or what we call lazy o2. what you could do is spray carb spray in the intake with a scanner
hooked up in live data for sensor 1. the carb spray should make the o2 spike rich if this
does not happen replace the o2 with a Nissan OE o2 sensor. do this a few times to see
the response. If it does spike every time then there is another issue.The EC section of the FSM should be able to help you. You can find it at
http://www.nicoclub.com/FSM/Sentra/2004_Sentra/ec.pdf
looks like the procedure starts on page 462
Update: I just want to give the results on this problem. I did get the flex pipe replaced (at a shop) months ago and put over 7,000 miles after the replacement of the flex pipe. The leak in the flex pipe was the problem because the engine light is gone.
[quote=”jspe8437″ post=179628]Update: I just want to give the results on this problem. I did get the flex pipe replaced months ago and put over 7,000 miles after the replacement of the flex pipe. The leak in the flex pipe was the problem because the engine light is gone.[/quote]
Glad you got it.
Hey guys,
I had a P0420 code for several years.
At the time, and with my lack of knowledge, I didn’t care about the P0420 code …I thought it was only emissions. The code IS for emissions, but it can ALSO mean other problems exist too! I’ll explain later.
So I drove it like that for maybe 35k miles, maybe 40k.
A surprise pregnancy (no. 5) sent us over the baby seat limit for our larger ride. Lol
Alas, we had to buy a new car …and sell my faithful Altima (now at 201,000). This made the P0420 code more of a deal breaker. I wouldn’t get as much with the engine light on.
And so began my journey to a CEL-free dash!
I started with Bluedriver. So glad I did!! I was able to see my fuel trims!!!! Life changing tool!!!
I was at 9% on my long trim and 17% on my short trim!! This meant I had a few leaks!
I was opened up to the world of not trusting CEL lights! Curse you Bluedriver!! Lol
I started with a starting-fluid-spray-test and found the first leak. Turns out when I had replaced my PCV valve, I had dropped a small ring gasket that sat in the PCV-hose-to-intake port. Fixed that and watched the STFT drop to 14%. Still not good enough. Read that a lot of Altimas have cracks in their exhaust header. Checked that and found TONS! TONS! There’s my problem!
Fortunately, the cracks and the P0420 code are the same part. My destiny was calling me! I had to replace the catalytic manifold to WIN! Lol
.
So I first tried a $100 aftermarket catalytic converter/exhaust manifold on Amazon. Didn’t even come close to fitting! Should have known.
Returned that and bought a $350 “OEM” one from O’Reilly’s. That didn’t fit too well either. Ugh!
Engine side heat shield didn’t fit, so I left that out. Had to modify a few heat shield holes for the radiator side.
Had to use spacers and different bolts to match the manifold mounting bracket up near the bottom. Finally got it in. What a pain!
Also found out that my exhaust pipe bracket had been squashed from coming down off a curb from our yard or something. So I replaced that and it helped the pipe meet up with the new manifold even more. Still wasn’t OEM though as O’Reilly said it was. Pshshh.
Anyways, so I started the car up.
P0420 gone! Boom. Within the first drive cycle! LTFT went down to 8%! So awesome! LTFT + STFT went to 9%. Nice!
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Here’s where the crap hit the fan!
The dreaded P1273 started popping up to say hi. Ugh!
Went through a few fuel trim clearing procedures (including unplugging the battery overnight) and it just kept popping back up.
Tons of sites were saying it was a lean issue. Injectors, bad sensors, yada yada.
Tried replacing my sensors a few times. Both upstream and downstream! Nope. It came back.
.
Found on YouTube that ONE mechanic was saying this code also popped up from an EXHAUST LEAK after the flex hose joint. I had remembered that after I installed the new converter manifold that the flex joint just didn’t feel as nice of a fit when I had put it back together. It was tight, but just didn’t feel right.
So I looked at that while the car was running and sure enough, noticed that I could hear the engine when I put my ear up to the flex joint. There was a smaaaall gap where O2 could get in and throw the readings at the 2nd sensor! Not enough to notice a huge difference on my Bluedriver (2nd sensor was showing 0.265 volts), but enough to supposedly throw my P1273 code.
So I installed a few rings around the male pipe connector on the manifold to help lift the curved side of the flex pipe gasket out a little further to fill up that gap I was talking about. After a few rings that I had cut out of a tin sheet I was able to make it mesh good to work with the new manifold and old flex joint and pipe. Bolted it back up. Started the car. No more noise.
The car sounded better than it had in a long time! No cracks in the exhaust, no flex pipe leak!
Performed the fuel trim history clearing procedure.
Man oh man I can’t tell you how pleased I am!!!! LTFT is 7%! LTFT + STFT hovers from 7 to 9%!
Been driving the car now for a long time and no codes!!! No P0420, no P1273!
Engine purrs!Here’s my final readings:
(range includes cold start to warm engine, at idle and 3000 RPM)
STFT 0 to 9%
LTFT 7%
O2B1 0.12 to 0.9V
O2B2 0.28 to 0.31V
So what did I learn? Here’s the main things that will change my mechanic life forever:
1. Catalytic converters should last for 200,000+ miles with a well maintained engine. If you’re cat goes bad, you probably have other problems that just haven’t thrown a code yet.
2. You can have small problems with no CELs that can turn into big ones!
3. Fuel trims can really help diagnose issues!
4. The 2nd O2 sensor is not JUST used for exhaust emissions! The ECM uses BOTH O2 sensors to determine fuel trims (and lean or rich fuel conditions).So what did this mean for me? That I will fix catalytic converter problems much sooner from now on if I plan to keep my car around past 200,000 miles.
If your engine is running rich for a long time it can damage other parts, and eventually expensive ones. I’ll admit, emissions aren’t my biggest concern. But I do care about engine longevity.
All that said, if you have a P0420, P1273, or P1274, hopefully my story will help save you some hassle.
Take care,
Benny
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