I'm hoping someone can help.

I've been getting a 'P0174 System Too Lean (Bank 2)' reading that trips the MIL intermittently. After reset, it seems to happen at least every day, usually when the engine warms up (and I think usually when I lift off the throttle, but not sure), and after reset may stay off the remainder of the day, or sometimes shows again. My gas mileage has dropped significantly.

I cleaned the MAF (and air filter since I had it apart), ran some injector cleaner in the tank, and did a visual inspection of the vacuum hoses (no leaks readily apparent). Is there an easy way to check for vacuum leaks, and if so, how likely is this since the MIL trips only intermittently?

I'm thinking it may be the O2 sensor. Mileage is only about 50,000 (80,000 km). Before I check the O2 sensors, I wanted to see if anyone might have some knowledge about this. Bank 2 is on the driver's side, correct? Would it likely be the front (pre-cat) sensor, or the rear?

Any other thoughts or suggestions?

TIA

 

Is the car stock or modified?? Need more info on the vehicle.

 

Had the mods on the car forever, so I don't think they are the issue. It only started throwing the code on the way back from vacation a few weeks back.

When the weather finally cooled down a bit last week, it seems to trip the code less than previous. Didn't do it at all on the W/E. Now it's back to once a day.

Engine/Exhaust mods:

GroundingGear® System, Motordyne Iso-thermal Spacer kit, Z-Tube, Fujitsubo Y-tube, Coupe mid-pipe.

Would an O2 sensor that is starting to go, trip the error code intermittently like this? I just wanted to be sure before I started testing them.

 

Seems to trip the MIL when the engine first warms up to operating temperature. After a quick reset as soon as it happens, the light will stay off for the remainder of the trip and until the engine cools down and has to warm up again, at least so far from observation in city driving. Sometimes, even during this cycle, the light will remain off.

So, any ideas, anyone?

Is this normal behavior when an O2 sensor goes, or should I be looking somewhere else? I have limited time to spend pulling the sensor/wires to test, so I'd prefer doing a more directed troubleshoot if possible. And if it is the O2 sensor, it would likely be the pre-cat one, and Bank 2 is on the Driver's side, correct?

TIA

 

i know the past doesnt dictate the future but the few P0171 and P0174 that i have seen on VQ were the maf. do you have access to odb software that you could monitor o2 voltage? that would show you if the tolerances of voltage are acceptable or if the sensor is completely not responding. i think you could rule out intake leaks since if it was significant enough to trip the light, it would be significant enough to hear.

 

I still need help guys!

I don't have OBD that will read the O2 voltage. I was going to just hook up a meter. But I suspect that since the MIL stays off for virtually all driving after the reset after initially tripping, the voltage would read normally otherwise.

I'd take it to a stealership, but because of the intermittent nature of the problem (other than the drop in gas mileage), they'd likely charge me for the usual diagnostics, and still not get a firm idea of the problem (though I could be pleasantly surprised), and may just end up replacing the O2 sensors anyway!

That's why I just want to know if I'm on the right track, and not needlessly replace the O2 sensor(s).

So, any good thoughts/ suggestions?

 

You have a PM Gord.

 

Hello, I was wondering if you could shoot me the pm....I am having the same code on bank 2 as well. This also has come about in recent cooler temps. It would be much appreciated.

 

Thanks Dave!

 

So, you're throwing the code on first warm-up as well, or is it more consistent?

Those that have changed the pre-cat O2 sensor, is it easier to get at from below or above?

Opinions on Bosch vs Walker vs Generic/OEM replacement? Universal vs Direct fit?

 

Mine is more constant. I saw it come on and stay on. I cleaned the MAF sensor and duct last night and cleared the code, we'll see what happens tomorrow.

 

I'm having the same issue with the P0174 error. It will turn off after a few days but will come back on. The only mod I have is an intake. I have no idle problems or driving issues that I am aware of. Can you please keep me updated on the status? Thanks.

 

I've been told by a couple of friends that I trust that work for various Nissan/Infiniti Dealers that jobber O2 sensors, and even Bosch aftermarket is not the best for our cars. They can sometimes (many times) cause problems or may fully solve what they should. MY buddy the parts manager said that NTK is the only one he'd recommend, and several of the forums suggest that the Japanese Sensors are better for Japanese cars, and Bosch is better for German cars.

I can get the OEM O2 sensor for a good price, but what is suggested is to have the error scanned by the Consult II which will show all other parameters that is throwing the P0174 code to ensure that it is the sensor.

Even if the sensor is replaced, they may have to re-program for the new sensor to work properly!

So I'm looking at an hour labour for the scan and diagnostic, another for the installation, and possibly another for the re-program.

So if I'm going to do this 'properly', it'll cost me 4 or 5 times what I had intended by changing the sensor myself!

Opinion? Should I just replace the OEM O2 sensor and hope the problem clears, or ???!

 

I cleaned the MAF housing, sensor, and intake piping up to TB, cleared the code and have not seen it yet.

 

i would agree with the bosch vs ngk but only with respect to spark plugs. if im not mistaken, bosch is oem for nissan. i have used bosch and walker brand o2 sensor on my past VQ with great results. i have never heard of need to program after an o2 sensor replacement. the only instance i can think of in my experience was an ecu flash on the maf after nissan replaced the previous part number with an updated version. if you have a good amount of miles on the car then it wouldnt hurt to replace an o2 considering you can get one less than 100 bucks from o2sensors.com most likely either bosch or walker.
is there any way you can find someone local with an obd2 scan tool that would be capable of monitoring the voltage? i certainly would not pay the dealership if they are going to follow that plan you listed above just from a cost stand point but id hate the idea of throwing money at part in hopes of fixing it as well.