A/F sensor, and O2 sensor, confuse

[turbocat]

Hi all, I need some light shed, on the subject of A/F and O2 sensor, are they 2 different beasts, or different names for the same sensor, also if they are different beasts, where is the A/F sensor usually located , and where is the O2 sensor located.

My care is running fine, just curious about these sensors.

1998 Maxima 99k miles

Thank you

[kzoosho]

U do realize that your a/f is dependent on your O2 sensors. On a stock car the ecu monitors the switching of them to try to maintain stoich (14.7) . If you need more info try google bro. All the info you will need is a finger tip away.

[loystock]

The MAF (Mass Air Flow) sensor (mounted in the air inlet duct besides the air filter box) and Oxygen sensors, together with other sensors are used by the ECM to meter the fuel (and air) going into the combustion chamber as well as ignition timing. The O2 sensors are not used (open loop) until the engine has been warmed up (close loop). Your car has Federal Emission configuration (not CA) and has 3 O2 sensors - Front Right (for Bank 1, mounted on the vertical section of Bank 1 exhaust pipe), Front Left for Bank 2 (mounted on the vertical section of Bank 2 exhaust pipe) and Rear O2 sensor (mounted at the rear catalytic converter. In general FRONT sensors are mounted before (upstream) of the 'cat' while the REAR is mounted after (downstream) of the 'cat.'

In the VQ engine, Bank 1 is for cylinders 1-3-5 and is close to the firewall while Bank 2 is for cylinders 2-4-6 are closer to the radiator.

[pm_page6776]

A/F sensors in newer nissans are just like 02 sensors. They do the same job but the A/F (air fuel metering sensor) is more accurate than an O2 sensor. A/F sensors are only used as pre-catalytic converter sensors. Most newer Nissans have A/F sensors in front of the converters and O2 sensors behind the converters. These are much different than a MAF (mass airflow sensor) This sensor measures the amount of airflow into the engine. In your maxima you do not have an A/F sensor. You have four O2 sensors and a MAF sensor. So for all you nissan guys, please do not confuse a MAF sensor with a A/F sensor. They are two completely different sensors. Even my parts guys get the two sensors mixed up when I ask for an A/F sensor.

[maxhopper]

You have four O2 sensors and a MAF sensor.

There are only three O2s in the 98 as posted above.

[pm_page6776]

You are correct, 3 sensors not 4. Regardless.... At least he knows the difference.
Modified by pm_page6776 at 1:56 PM 9/10/2009

[turbocat]

Thank you for answering, now i know what is going on, i couldn't find any info on the a/f sensors, i didn't know the newer nissans were using those, and using 02 sensors downstream, thanks again