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Discussion Starter · #1 ·
Hi boys. I need your expertise. As some of you might know, I had my timing advanced from 15 to 17 degrees last week and I only run 94 octane gas. This weekend, I got 2 SES lights for fuel sys lean b1. I erased the first one with the gas pedal procedure, but I can't get rid of the second one.

Anyhow, it's the 5th SES light in only 4 months since I've had my ride. It's always the same error code FUEL SYS LEAN B1. The mecanic at Nissan says it's normal because when he checked with the Consult-II, it said that my second O2 sensor (the one relocated on the catback) wasn't getting proper reading because I have no restriction in my airflow because I have the 2.5 inch piping from GReddy Evo 2 catback and that my air/fuel ratio will be lean...

I also tried setting the Dat2 file on my A'PEXi S-AFC II (file 2 is factory settings, no tuning done) and the light still came on after that... I'm so worried and I don't know what to do... Anyone have suggestions? Is this normal? Should I be worried?

Hope you guys can help... (For a list of my mods, check websites in my sig).
 

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ummm im no mechanic but from my understandeing, Lean=Detonation
 

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Lean is probably an o2 sensor error.

If you feel like spending the cash, try replacing the first sensor. That one does most of the readings. If not, try and convince your dealer to replace the first o2 sensor. The 2nd o2 sensor will give you a 0420 (cat efficiency) or another error I think it's 0032 that is essentially the o2 sensor not working at all..

Detonation should have a different code than stating it is running lean. just for schits and giggles, you might want to disconnect power to your amps and see if the code goes away, maybe there's some kind of ground loop causing bad readings?
 

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Discussion Starter · #5 ·
The error code is 0171 and it says FUEL SYS LEAN B1

I hope you can help me cortrim1... You know your ****! ;)
 

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dtc p0171 fuel injection system function

sensors
heated 02 sensor
air fuel ratio sensor

condition
*fuel injection system does not operate properly
*the amount of mixture ratio compensation is too large(out of spec condtion-lean)

cause
*intake leak(after maf)
*02 sensor not functioning properly
*air fuel sensor not functioning properly
*injectors
*exhaust manifold leak(before primary 02 sensor)
*incorrect fuel pressure(bad fuel pump or regulator)
*lack of fuel
*maf is not reading correctly
*incorrect pcv hose connection.


figure out when you first got the ses light and go back to the mod done before the light. if you got this with a totally stock car take it to the dealer and make them fix the issue.
 

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Discussion Starter · #7 ·
My car is only 4 months old. I had I/H/E and never had problems. The first time I got a code was RIGHT AFTER the S-AFC II installation. But the funny thing is we only corrected -2 to -4% from 4800-5800 rpm, which isn't big at all. I cleared the codes a couple of time and it seem to disappear, until I had my timing advance last week (to 17 degrees) and the next day, boom, the code came back.

I don't know if this can help, but it seems the code appears when the car has only been running for 5-10 minutes and that I accelerate hard and then set it to cruise control (around 100 km/h) on the highway...

Does the fact that I have a 2.5 inch catback can cause problems with SES?
 

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Discussion Starter · #8 ·
Cortrim1, with what I've given you as info, what do YOU think the problem might be?

The car is spankin' new... I know things can break anytime, but I mean come on, what are the chances... There must be something somewhere... Like that sound I was hearing around 2500-3000 rpm. It's now gone, we solved it.
 

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lawngn0mex said:
Lean is probably an o2 sensor error.

If you feel like spending the cash, try replacing the first sensor. That one does most of the readings.
how much is it for the first sensor, would it be wire and the sensor part cause i think thats why my ses is on, cause i had spliced into it to put a/f gauge on (which i took off)
 

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the 04's are programmed to run as close to stoich as possible. This error is stating that its trying to stay with in the factory a/f spec but the amount of fuel needed to do that is too large per the normal operating range. this may be due to a bad install(high restistance on maf connection) or the unit is not setup properly. Also if the wideband used to tune the car was off you will have these issues. tail pipe wideband sensors are know to give reading that are off because of their location. for a proper reading you would need a wideband to be inserted in to the collector on the manifold. I would remove the spark plugs and check their color. if they are white you are running lean.
 

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Discussion Starter · #12 ·
My S-AFC II was tuned with a wideband O2 sensor inserted in my header (instead of the 1st O2 sensor). So I don't think the reading were off (plus like I said, we only made very slight changes in the A/F)...

Maybe as you mentioned cortrim1, when I had my timing advanced, that made the car run leaner. And even if I switched to the dat2 file and got a code, I probably didn't give the ecm enough time to reset the long term fuel maps to see a difference (I had the timing advance done last Thursday and the codes came Friday and Saturday).

???
 

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Just to try something put your S-AFC setting back to zero (no corrections). See if that makes a difference. As Contrim1 stated dyno widebands can sometimes be off, even the ones that are inserted into your manifold.

Also, when they removed the first O2 sensor at the dyno to insert their wideband did they have an output wire that provided reading to the ECU? They should have connected a harness to your motors O2 sensor. If they didn't do this, your car bay have been running rich (because it was not seeing a reading from the O2 sensor). If they tuned the AFC while the motor was running rich, then that may cause a lean condition when the motor is running properly.
 

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Discussion Starter · #14 ·
Can the code go away by itself after a week or two if the ecm has had time to adjust itself or do I need to have it cleared ABSOLUTELY by a Consult-II for it to go away?
 

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OrangeVee said:
Please stick to my questions boys.
no stick to MY question, this is my thread to hijack ;) j/k ill go ask my question elsewhere
 

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Discussion Starter · #17 ·
Ok, so I had my car checked at Nissan tonight with the consult II. The error code was again 0171 fuel sys lean b1. They checked info and it mentioned the code was thrown (as usual) at 3000 rpm at 122 km/h (around 76 mph)... How weird is that? And they took out the spark plugs to see if I was really lean, and the plugs were white. The 1st O2 sensor (on the header) reading was fine, alternating between rich/lean. The 2nd O2 sensor (relocated on my catback) always indicates lean. Could this be because of my 2.5 inch catback? Too much airflow and no resistance so no time for the sensor to do proper readings? Also, the engine running temperature was 87 degrees Celcius (around 188 degrees Farenheit I think) which is quite normal I think. I put my S-AFC II to the dat2 file (stock) to see what will happen.

Does anyone know why I'm actualy running lean now with these new informations? And if I have the stock file running on my S-AFC II, is the S-AFC II still modifying stuff, hence still has the chance to send an error code? Thanks.
 

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Is the dealer has pull back timing to stock and of course cleared all the codes?

And for the SECOND O2 sensor, first it don't play any role in term of A/F ratio calibration and second, it should read always lean because the catalyst before it will burn remaning fuel and prooving the the ECM that their is a cat doing the job... if the reading would be the same on both O2 sensors, then there would be a problem :confused:

I think the problem is related to the SAFC-II... get rid of it and give it to me :p
 

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Discussion Starter · #19 ·
No the mechanic left the timing advanced to 17 degrees. I'll try running on the data 2 file (stock) on my S-AFC II to see what happens...
 

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OrangeVee said:
No the mechanic left the timing advanced to 17 degrees. I'll try running on the data 2 file (stock) on my S-AFC II to see what happens...
I was thinking about this after we PMed eachother and I was about to sleep. Your 02 wires are extended.. what kind of wire did you use? Also, did you use butt connectors or solder and shrinkwrap? Reason I'm asking is because if there is more resistance in those wires through that connection it can cause you to go lean...

The o2 sensors are narrow or 1v o2 sensors. At full they run at 1v signal, and at closed it's at 0v. If the resistance in the signal wire (black IIRC) is high, or the ground (gray) is high, it can alter the signal and tell the ECU you are running too rich, and then it will compensate by leaning out the fuel.

Also, IIRC the 2nd o2 sensor does affect A/F in certain driving conditions, which would explain why it's intermittent, and you can repeat it by repeating that specific driving condition. I would redo your o2 extension connections first thing, or redo them with higher grade wire, if they aren't the best wires.
 
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