This is a little more technical then what I’m used to in a while. My 2005 Infiniti G35x with 71k has been having a on and off CEL for the past month. P1283- Air fuel ratio sensor 1 lean shift- bank2.

It comes and goes, like I can drive 100 miles and it would never light up and I can go 15 miles and its always on. Car runs great. MPG seems to drop about .5 MPG but then again its winter blend fuel time. I didn’t see the CEL for almost 2 tanks of gas (300 miles per tank), then I filled up with a tank of Sam’s club gas. Within 10 miles, it was on with the same fault. And it would repeat say every 15-25 miles. I ran down that tank instantly and got to Mobil. Full tanked it on 93 octane, it was good for the first 100 miles and now it’s back again. Here is a kicker, it will set the readiness code almost everytime! So I can still pass emissions in my state pending on time I take it in.

I have an android phone with the torque app, so I set it to graph the both front 02 sensors. First thing I see is bank 1 being at 0.3volts and bank2 being at 0.5v. I take it for a drive to watch the voltage to see if I have one of those LAZY sensors. Aside from the difference in voltage I noticed bank 2 would spike up more than bank 1 and in most cases it would hit .9-1.2v and the most bank 1 would hit is .7v, this is me gunning it and letting off.

I assume me letting off triggers the lean condition and the higher voltage is leaner and lower voltage is richer.

Would it be safe to say I have a soon to be dead bank2 sensor? Is there any testing I can or should do? I always thought .5v was a good idle voltage and not .3v

 

I am seeing almost exactly the same indications from my G's A/F ratio sensors. I have a pretty much bone stock 06 G Coupe Auto at around 92K miles. I have had NO CEL indications what so ever (no fault codes either), however my Bank 1 A/F is at .3 volts during normal cruising while the Bank 2 sensor reads .6 volts. Both of the downstream o2 sensors read about .8 volts. During deceleration, both o2's drop to zero volts while the Bank1 A/F rises to .7 to .9 and the Bank2 A/F rises to 1.1 to 1.3 volts. Again that left sensor is about .3 to .4 volts lower while the o2's read the same. WTF this cannot be normal.

Oh and to add to this I have the usual annoying light throttle ping coming from my engine, regardless of the fact that I am using 93 octane. One thing I have noticed is that the ping doesn't seem to exist until the torque convertor locks up, therefore adding additional load to the engine. Also par the usual these engines don't knock until sufficient heat soak has reared its ugly head. I'm wondering who else on here has the same odd difference on their A/F sensors with no CEL/codes and no discernible powertrain issues besides the ping? If the A/F sensor voltage imbalance is an issue what is causing this?

As I have seen from experience just because your Oxygen sensors are not reading correctly does not mean one or both bank's sensors are bad. There are other sensors directly related to fuel delivery, the MAF for one.

Has anyone with the pinging tried having their fuel injectors pulled and bench cleaned? With the crap they put in gas these days who knows what kind of residue gets left behind. In tank treatments are worthless and do more harm than good, the ones that hook up to your fuel rails are, from what I have heard, worse as these can break the junk apart in your injectors and cause them to lodge somewhere more critical thus making the spray pattern worse.

If anyone has any thoughts about this lets hear them.....

 

have you guys checked out the a/f alpha readings for both banks?

 

Loose plenum bolts? Only time I have ever gotten a lean condition light. Are there any mods?

 

My G sedan is at 105k with ART Pipes, a Borla exhaust, and a Stillen intake. I just ran a code check this morning and it returned this. I'm in the same boat as you; car runs perfectly fine, no noticeable decrease in mpg. I get my gas from the same place and only got a CEL maybe a week ago. I haven't done any voltage testing yet though. Is anything actually like fatally wrong here?

 

^^With the breather mods you have, your car is running dangerously lean. Your motor's sucking in more air than your ECU can compensate for so my advice would be to get tuned with Osiris as soon as you can. It's a little pricey but worth every penny.

 

So basically these mods are kinda running my car into the ground

 

Not necessarily, but you would really benefit from a tune

 

What about this a/f alpha readings? I'm pretty sure that the A/F's shouldn't be reading .3-.5 volts difference from one another for any reason. So what is going on here, is the Bank 2 sensor improperly registering Bank 2 as rich and the ECU is leaning it out causing the ping? What are the A/F's supposed to register with the engine fully warmed at cruising speed, at light throttle.......Is this a possibly unknown issue with the G and pinging, as far as a/f sensor imbalance or lean bank possibly being the culprit?

Would this Osiris tune help with that or is this one of those issues that needs to be "fixed" first? Mind you I have never seen any check engine light on this car except for an idle out of threshold or whatever and that was because I didn't move the car for a month, instead I ran the engine every week to keep the engine from drying oil of all of the parts (yes I know this is kind of silly), I think that pissed off the ECU into thinking something was wrong with the APP sensor.....

 

I've never paid attention to the voltage so I can't answer that, I always just datalog the actual air/fuel ratio. If you can get your hands on an uprev cable you can monitor and record all that, so you will know if its actually running lean, has a bad sensor, or is something that you should just ignore. If it was actually running really lean (or had a bad sensor causing the ecu to think its lean and dump fuel in making it run rich) it should throw a CEL..

 

TurTLe sir! Good day... favor to ask as I'm going thru same deal! What did you find fixed this A/F sensor prob. Would you let me know please??? Tks so much... very much appreciated!
-r

 

Last time I saw that code I changed out the driver side af sensor and that fixed the problem.

 

Hey BytheBay! First thank you so much for your videos and posts!!! Seriously thank you! changed my plugs, pcv, both camshaft pos sensors. HUGE amount of help!!! So great. Ok, seems like everything is leading to that sensor. My code poppin up is P1273 but think it's same. Embarrassing question... is AF sensor same as the O2 sensor?? Ok really tks again! I and many others owe you.

 

The af sensor looks like an o2 sensor from the outside but unlike an o2 sensor, it is pre-cat.

 

Back to the top! This code came about a month or so ago and I was fairly certain the car had no leaks on intake/exhaust setup so I went to get my mods dialed in via Osiris tune at Z1. We got nice gains and everything seemed to be running good. However the 1283 an occasionally a 1273 code gets thrown for a lean shift condition. Any ideas as to how to address this considering it has appeared on both banks from time to time? I feel like it's the mods but thought the tune would take car of it. I need to run it through emissions (obd check) and need this solved. Any input is greatly appreciated. Engine related mods are rev up air box, CF Z-tube, skunk2 5/8" spacer, Megan resonated test pipes, and invidia Gemini exhaust.

All plenum bolts are tight and center bolts were sealed up. Vacuum tubes seem in tact. Intake tubing tight.