# Codes 1273 and 138, O2 bank locations, help



## Narco944 (Nov 4, 2010)

My wife's 04 Maxima is failing emissions. We took it to the dealer and they wanted $1100 for repairs. Negative. I'll try this myself. Here is what their paperwork reflected:

code #1273 - air flow system sensor failure

code #138 - oxygen sensor failure B-2

mass air flow alpha sensor readings AIN the lean percentile

their recommendations: air flow sensor replacement $480
O2 sensor replacement $375
fuel econ system service $170
idle control system relearn service $95

From what ive been reading code 1273 is any number of things. Some say O2 sensor, some say its the MAF. Does anyone here know for sure?

Also, code 138 says O2 sensor failure B-2. How do I know if this is BEFORE or AFTER the cat?

Im also confused as to where B1 and B2 is on this car. I know B1 typically is on the passenger side but as I look at the motor up top I see an O2 sensor behind the radiatior and another on the driver side of the motor. Which is B1 and which is B2?

I'm sorry this 1st post is so long but I gotta get this fixed ASAP. I feel like all the ATL area dealers are out to hose you. I spent 40 minutes on the phone with Conyers Nissan and no one could answer these questions for me.


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## Nickaltima (Jan 11, 2008)

1st off go on ebay and get a maf sensor they go for around 60-100 bucks new and its easier to change then putting washer fluid in lol really it is sooooo easy..10 mins tops with hand tools also the idle relearn is available online i have it and keep a copy of it in my car i can send it to you but it is very tricky to do you have to do things at certain times and they have to be 100% precise on timing also there are 4 o2 sensors on the car and all but 1 on the back exhaust manifold are easy to get to for replacement..the only thing is they are tough to get out sometimes you need some good penetrating oil and good leverage but very easy to change agin for even an inexperienced person..i hope this helps ya if you have any ?s feel free to ask or pm me man


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## Nickaltima (Jan 11, 2008)

oooo and i forgot bank 1 and bank 2 have nothing to do with sides it is the positioning of the sensor according to where the catalytic converter is bank 1 is pre cat bank 2 is post cat


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## Outkast (Jan 29, 2006)

Nickaltima said:


> oooo and i forgot bank 1 and bank 2 have nothing to do with sides it is the positioning of the sensor according to where the catalytic converter is bank 1 is pre cat bank 2 is post cat


Wrong, Bank 1 is the rear head and Bank 2 in the front head. 
o2B1S1 means the rear sensor before cat 
o2B1S2 means the rear sensor after cat
o2B2S1 means the front sensor before cat
o2B2S2 means the front sensor after cat 

If the tech watched the voltages on the MAF he could tell if it's bad. The 2 codes combined can more likely mean you have a small vacuum leak. The computer is just assuming either the signal from the MAF is wrong or the o2 is bad.


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