Hi all,

I have a P2A00 code for at least 1 month now and I'm totally out of idea. P2A00 code is : Air Fuel Ratio Sensor Circuit Range/Performance - Bank 1 Sensor

Short story prior getting the error code : While driving, the O2 sensor literally popped out of the catalytic converter (on bank 1) ! So my mechanic did some welding, and he put back the O2 sensor in its place. He also took a voltage reading on the 02 sensor just to make sure it was still ok.

However, the P2A00 error code came back a few days later. So here is what we did so far.

- after inspection, the OEM Intake tube was cracked somewhere. So I changed it with a Z-Tube from Z1motorsports. Did all the reset/relearn procedures then cleared the error code. It came back a few days later.

- Smoke test was done by my mechanic to check for any exhaust leak.Everything is sealed correctly.

- front O2 sensor on bank 1 (near the manifold) was replaced. Did all the reset/relearn procedures then cleared the error code. The error code came back later. 300 bucks down the drain.

- rear O2 sensor on bank 1 (near the catalytic converter, the one who popped out) was replaced. Did all the reset/relearn procedures then cleared the error code. The error code came back later

- I also put a injector cleaner in my gas tank but it didn't made any difference.

So for now the code is still present, my mechanic is out of idea and he said that at this point I would need to have my car inspected by the stealership.

Any help would be appreciated !
(btw sorry for my english ! I'm from Quebec)

 

The front sensor is not an O2 sensor it's an Air to Fuel ratio sensor. That code probably has nothing to do with the rear O2 sensor popping out. The rear O2 sensor just monitors the efficiency of the catalytic converter.

Did he use an OEM part(s)? What diagnostic steps did he take prior to replacing that expensive sensor?

Did he check the voltages, resistance, etc... before condemning the sensor?

Were your fuel trim levels looked at to make sure you don't have a vacuum leak or running rich?

That can be caused by vacuum leaks, wiring, bad sensor, bad heater on the sensor, fuel pressure, etc...

 

Hi coffeysm, thank you for your input.

the mechanic changed the front A/F sensor after looking at every other things that could lead to a P2A00 code (intake leak, exhaust leak, swapping rear 02 sensors from bank 1 to bank 2, cleaning injectors, cleaning MAF). I'm not 100% sure if he looked at the voltages and or resistance before changing it. I think he changed it as a last hope to fix the issue ... The mechanic ran more tests after changing the A/F sensor in order to find the issue without billing me for the time he spent looking at this (knowing that I just have spent 300 bucks for nothing) ...

Anyway ... If I look at the SFT, the bank 1 is running rich VS bank 2. About +10% of difference. Bank 2 seems to be around 0 most of the time but Bank 1 is always higher. It never goes down below 0% like bank 2 does. I might have to double check for a vaccum leak somewhere ...

As for the new sensors, they have the right voltage and right resistance, according to my mechanic. However I'm not sure if he used OEM ones when replacing them.

 

What are the actual numbers and what are the long term fuel trims as well? Are they positive numbers or negative? If they are negative then your car is running rich and probably doesn't have a vacuum leak, I'd look at fuel on that bank. If the numbers are positive than it's running lean and I would look for a vacuum leak.

What about your MAF what are g/s it's showing? If you have a bad MAF it could be giving false data to the ECM. I think it would show up for both banks though.

If you unplug the MAF and read your fuel trims it should run rich at -25% both banks. It will set a code though.

 

SFT at crusing speed (in town) is around +10% on bank 1 (positive value), and around 0% on bank 2. So bank 1 is running lean and not rich (sorry for the mistake in my previous reply). Bank 1 can peak up to +25% when I release the gas pedal after going WOT. Bank 2 never goes above +10%.

As for the MAF, I don't think it's the culprit. Like you said, it would give me another error code for bank 2. However I haven't tried to unplug the MAF to check if both bank would be at -25%.

I just went to pick up my car at my mechanic. He said that he cleaned the fuel injectors and fuel rails this time. He also did a few other things (cleaned the solenoid screen for the VVT if I reacll correcty) as well as checking the spark plugs and other things. He didn't charge me anything.

I will look for a vacuum leak somewhere. But as far I can see, I cannot find anything that is obvious.

I guess I will have to send my car to the Infiniti dealership. I will update this post when I will have some news ...

thanks again !

 

If you're running lean when cruising I don't think a vacuum leak would impact it all that much.

How about your long term fuel trims (LTFT)? Those are the base settings for your fuel.

You MAF should be reading 2-6 g/s at idle and 7-20 g/s at 2500 RPM.

Did he check your fuel pressure? Usually, you have to tap into the hose to get a reading.

Can you read the voltages for B1S1? When in closed loop revving around 2500 RPM. It should fluctuate a little bit around 1.5v.

What year is your car?

 

I can't give you LTFT right now. I will need to take a ride to have accurate values.

As for the MAF readings. I have 4.2g/s at idle (around 900 RPM) and 11g/s at 2500 RPM.

As for the fuel pressure, my mechanic haven't done this test I guess. He told me the fuel flow readings on each injectors were all equal. He also did some test by sending pulses to the injectors and they were responding correctly.

As for the B1S1 voltage, I'm note sure which one to look at. They are identified like this in my app (OBD Car Doctor)

O211 (Bank 1)
O211 (Bank 2)
O212 (Bank 1)
O212 (Bank 2)
O221 (Bank 1)
O221 (Bank 2)
O222 (Bank 1)
O222 (Bank 2)

So looking at each one which is "Bank 1" :
0211 = 0.22V
0212 = 0.28V
0221 = 0.57V
0222 = 0.34V

noting as close as 1.5V.

I will try to do some research to find out if I can read the B1S1 voltage with my app.

Thanks,

 

and my car is a 06 G35 Coupe 5AT (VQ35DE)

 

I have the same year and model car. I'll try reading my values and see what I have. I was going through the fsm and there is a procedure for removing not just dtc, but emission related data. You unplug the maf, start car for 5 secs, turn it off, and turn it back on. Then you need to switch to diagnkstic mode by doing a pedal dance to remove stored emission data. You could also unplug the battery for 24 hours. I usually unplug the cables, press the brake, and then touch the cablss together. To get rid of any residual current.

 

Try holding the cables together disconnected from the battery for like 10 mins. Then do the maf unplug/plug step that will trigger the car to do self relearn.

 

Just thinking outside the box a bit but do you have any shift issues with the auto transmission, shifting early and lugging the motor or failing to downshift properly when slowing back down can completely screw your A/F ratio as well, but it doesn't typically cause a static change from one bank to the other like you're experiencing. I would also check electrical resistance between the ground wire of the passenger side A/F sensor (bank1) to the negative battery terminal to verify there isn't a bad chassis ground on that part of the exhaust system.

Verify with the mechanic that they're working on the correct sensor and not accidently working on the driver side one.

Lastly, what engine mods do you have?

 

I'm also wondering when you said your rear O2 sensor popped out did it hit the ground or get damaged somehow? Maybe it's giving false information back to the ECU about how the CAT is running or not responding fast enough anymore.

 

Hi cleric670

no shifting issue as far as I can tell. The car is bone stock.

I just spent 4h of diagnostics time at the Infiniti dealership (at 130$/hour of labor time) and they did not to anything ! Lol what a joke ... They made sure that the resistance and voltage were ok on the a/f sensor and they did also another smoke test on the intake and everything was fine. They looked at the tech db and they haven't found any similar issue ... wtf

so for now I will try to do the maf unplug replug as suggested and let the car sit for a few hours without the battery. I will also check for any grounding issue.


Thanks

 

Any update on this? Anything end up working for you? I am getting the same code and have taken it to my tuner to check for leaks, replace sensor, clean MAF etc.

 

SES still comes on every 100-700 miles. Mods are below. I am at a loss for what it could be at this point.

06 6MT <40,000 miles as of this post
MD 5/16 spacer
MREV2
Z-tube
Berk HFC
HKS catback exhaust
Uprev Dyno Tune after all parts installed