'07 Altima 2.5 P0137

[Towncivilian]

My mother's 2007 Altima Sedan 2.5L is getting P0137, "O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)". I'm having trouble locating exactly where this sensor is using the FSM, anybody know the page in the FSM or can tell me where it is? Is this the correct replacement part? Will an aftermarket part work?

[QR25DE]

Secondary O2 sensor. It's under the car in the exhaust system by the 2nd cat. Check the connection on it. It could indicate the cat is bad as well or not working efficiently.

I would suggest simply clearing the code. Low voltage could have been triggered by a few things.

http://www.obd-codes.com/p0137

[Towncivilian]

Code came back after resetting.

When my brother owned this car he went through several O2 sensors, which were replaced by Nissan under warranty. There's no warranty anymore. It seems as if something is causing the O2 sensors to foul and Nissan just treated the symptoms (bad O2 sensors) instead of finding the root cause.

What should I try now?

[wade001]

sounds like the car is running rich, the extra fuel could be melting the O2 node. not sure if it is after the cat but a rich fuel mixture is not good for the cat either. hows ur milage?

[Towncivilian]

Not sure about the current gas mileage. My father decided to forgo changing the O2 sensor. I'd gladly swap it out with a new part, but it's ultimately his choice. Like I said, the car ate O2 sensors before (and I confirmed this with my brother) and it'd probably just eat another one within 6 months. The car has about 80k miles on it, my brother put around 75k on it in the 3 years he had it. I'm sure if the car is running rich as a result of this bad O2 sensor it's not good for the engine, but ehh...

[wade001]

running rich really wont effect the engine much, but your O2 sensors and cat will go bye bye. and if the melted cat internals plug the exhaust ur engine will eventually take a sh*t as well. earlier altima 2.5s had this problem i think.

[QR25DE]

Yeah this could simply be a symptom of a bad/non-working catalytic converter. It's not burning the excess fuel thus fouling/ruining the o2 sensor. If you can, see if you can borrow a wideband sensor from someone and see what the air/fuel ratio is. If it's rich (12's and lower for N/A) this is the cause.

Tap the cat with a hammer lightly, do you hear pieces rattling around? I wonder if it's separated and falling apart... you can try the 35 dollar o2 sensors from ebay as well. I know a few people that run them for secondary o2's in other cars and they seem to work fine *shrug*. Honestly, the 2nd o2 sensor is "meh". I wouldn't worry about it too much to be honest, but i'd check the cat for sure.

There are two cat's on this car, one on the exhaust manifold and the second right before the 2nd o2 sensor. The 1st one is the one that's know to break apart but check both. I don't run a 2nd o2 sensor as I have my wideband in that bung and I have disabled the code for it lol.

[Towncivilian]

Bit of a bump here. I have a USB ELM327 OBD2 scanner and the ScanMaster ELM software which I believe can read the air/fuel ratio, so I'll take a drive in it and see what it logs. I'll also get a rubber mallet and tap the cats next time I get an opportunity.

Like I said this car has eaten several O2 sensors while under warranty if I recall correctly. I'm unable to find the maintenance records for those though.

[QR25DE]

[quote="Towncivilian"]Bit of a bump here. I have a USB ELM327 OBD2 scanner and the ScanMaster ELM software which I believe can read the air/fuel ratio, so I'll take a drive in it and see what it logs. I'll also get a rubber mallet and tap the cats next time I get an opportunity.

It may be able to read o2 voltage, but I'm pretty sure it doesn't read AFR. The ELM327 is kinda limited when it comes to that stuff. Let me know though. Curious. Had one myself and used ProScan.

[atlM35]

Another option:

gut the cat and buy an O2 sensor off ebay for $5.
better exhaust flow and no more worries.

[QR25DE]

Another option:

gut the cat and buy an O2 sensor off ebay for $5.
better exhaust flow and no more worries.

This will do the exact opposite. My previous suggestions stand.

[Towncivilian]

While Florida does not have emission inspections, that is something I definitely will not do. It's not my personal vehicle and even if it were, I'd still refrain from doing so.

I don't have a laptop with a functional battery so it may be a while before I'm able to drive the car while logging with ScanMaster.

[QR25DE]

Cool, well keep us updated .

[Towncivilian]

I'm pretty sure my scan tool can't pick up the necessary AFR.

I'll remove the oxygen sensor at some point and look at it to see if it's visibly defective. Can O2 sensors be cleaned somehow?

My brother said that he thinks the other three oxygen sensors were replaced under warranty, not all the same sensor as I previously thought. Still, $140 for a part that will essentially make the SES light turn off doesn't seem worth it to me. I've read that the rear O2 sensor(s) don't do much but verify that the cat is working properly, correct? If a cat was bad wouldn't I be throwing a P0420 and more O2 sensor codes? I figure as long as I check the codes monthly to see if any others pop up, there's no reason to change the sensor assuming I'm correct about this sensor's function.

[Towncivilian]

I acquired the entire service history for this vehicle and it had one O2 sensor & cat at 35,008 miles, and one rear O2 sensor replaced at 44,743 miles, all under warranty.

I still haven't checked the connection of this O2 sensor - the car's due for an oil change in about 500 miles so at that time I'll look for the sensor and verify connection and wiring. Where exactly is it found?