Have this code.
Did the automatic, gut reaction thing, and installed a new AF sensor.

Code Came back.
Note - there is a rich smell of gas on start up and it continues...

Data:

With my Foxwell Tech Scanner was able to see interesting data.


B1S1 AF/S @ ~1.45 B1S2 @ ~0.7V - HTR=OFF
B2S1 AF/S @ ~1.45, B2S2 @ ~0.7V - HTR=OFF
Everything seems in "balance between B1 side and B2 side".

B1 injection pulses are 2.5ms (always 0.2ms higher than B2 throughout the test). Fuel trims are higher.
B2 injection pulses are 2.28ms (always 0.2ms lower than B1)
Would this mean that that B1 is supplying RICH mixture to combat LEAN condition, continually?

After the HTR=ON everything on B1 changes...

B1S1 AF/S @ ~1.29V. Never reaches 1.45V.
B1S2 @ ~0.11V*
*oscillates but stays at lower voltage throughout running RPM.

Does the B1S2 low voltage means that it is actually reading correctly - higher fuel pulses - attempt at rich mixture but I have a lean condition?

Of note:
B1S1 never achieves 1.45V after HTR=ON.
Always stays below, around 1.29V, never achieves 1.45V throughout the test after the HTR=ON

When B1S2 oscillates, primarily staying in low voltage throughout.
B1S2 never stays at a constant higher voltage when the pedal is pushed down. It stays low. in 0.1, 0.2 range.

Assumptions:
If there was a leak between B1S1 and B1S2 -
B1S2 readings would normalize to see a higher voltage output (when O2 is added, drawing air through a gap in the exhaust, if there were to be a leak there).
I'm ruling out an exhaust leak - for now.

Old and New behaving the same:
As I have the same code with a new and old sensor - it must be a wiring issue between the ECM and the AF1
I would have to check grounds, and the HTR circuit continuity and power at the connector, prior to looking at a fuel issue.

Fuel:
I am assuming that longer pulses mean more fuel. The Lamba is at 115% on B1S1.
But, the low voltage (.1 - 2 V) at the B1S2 means - high Oxygen under throttle - meaning LEAN mixture?
Do I have a fuel delivery issue - injectors?

I performed a power balance test, disabling one cylinder at a time, and the response from each seemed the same.

Method:
My first check it to verify the wiring to B1S1 is good prior to investigating anything with fuel?
Would a failed HTR circuit cause all of this with the AF sensor?



Thanks for anyone's insight. Sorry, I don't have the graphs. I hope this makes sense.

Your A/F sensors are centered at 1.5V and biased at about 0.3V, rich is lower than 1.5V and lean is higher. So there's no way either one should ever be reading 0.11V. That equates to about a 10.5:1 mixture, which is not even in the real world. The heaters have a common supply and share a common ground inside the ECM, so I'd say the most likely explanations are an incorrect replacement sensor or a lot of crossed wires between the heater and data circuits.

Sorry the .1 - .2V observed, is on the B1S2 O2 sensor only.
That voltage stays low throughout. It seems to move when the AF ratio voltage bumps around a bit.

Sorry for any confusion

B1S1 never reaches 1.45 after the HTR is ON, it stays around 1.20-1.29V
I forgot to add that the B1 S1 Lamba always stays near 113-115%, never drops to 100.

Editing:

Would it be correct to assume I have a significant leak in the exhaust?

If I am reading 1.29 at the AF sensor (rich), and then (0.1-0,2V) at the O2 (lean), then perhaps I have to have a significant leak between the two sensors....

My bad, I misread that. The 1.29V is slightly rich, about 14.0:1 (ideally should be 14.7:1). The ECM does cross-check S1 vs S2, so an S2 that's flatlined after the cat is "lit" can cause P127x/P128x codes. The S2's should both be switching once you raise the RPM's with the cats lit, from below 0.3V to above 0.6V at about 1/2 Hz frequency. If the sensor is flatlined at 0.11V when you're cruising or high-idling then either the sensor is shot or the heater is inoperative (although not open-circuit, that would throw a different code). I'd try a new rear sensor before looking for leaks.

Wait a sec...
IMPORTANT: Did you clear out the self-learning data after replacing the A/F? If not, pretty much all the P127x/P128x codes will keep coming back even though the problem is fixed. If your scanner has work support for clearing LTFT then you can do it that way, otherwise pull the MAF while the engine is running until the ECM throws a P0102, then stop the engine and clear the code. If that doesn't help, then try a new S2.

100% I've performed the MAF pull.
I think I did it 3-4 times, going through the Nissan Manual process.
I did receive the P0102 code, etc.

Thanks for your input!

B1.S2 it is.