P1148 A/F Closed Loop Bank 1

[dahomietaz]

New here!!!! First post ever being made on here so hopefully I am in the right spot. So let me explain my situation.

I have a 2007 Infiniti G35X (VQ35HR) and i am FBO Tuned. LTH, Long Tube Intakes, Full Exhaust, Admin Injectors and 340 FP.

So i loaded up the software Uprev on my computer for data logging and noticed that both upstream A/F Bank 1 Sensor 1 & Bank 2 Sensor 1 were not reading. So i replaced them with OEM O2 sensors. Loaded back up the data logging and saw that after installing the brand new OEM O2 sensors, they still aren’t reading. So after doing some research, i found that there is actually a O2 Sensor fuse for our cars that is directly behind the battery. (yes you have to remove the battery to gain access to it). The fuse is a 15A mini profile fuse. After i replaced that fuse with a brand new one, i hooked everything back up, got into my car with my computer and started to pull some data and saw that the issue STILL WAS NOT FIXED!!! At that point, i realized it wasn’t a fuse or a o2 issue. It was either a ECU issue or a wiring/harness issue. By chance, i had a backup ECU laying around and at the time when i got it, i had it unlocked to work with my key fob. i hooked up the back up ECU that btw i have never used before or had programmed and all of a sudden, BANK 2 SENSOR 1 works!!!!! Looking at the data log, BANK 2 SENSOR 1 reads BUT Bank 1 Sensor 1 is still not reading. So i’m gunna make the assumption that this is a wiring issue. 1 or more of the 4 wires (not on the o2 sensor) on the connector from where you plug the o2 sensor into is broken. So after telling my little fairy tale, i was wondering if anyone would know where to start??? I cannot find online which of the 4 wires are ground, signal, heater circuit, anything really. But seeing i am getting nothing from the o2 sensor (once again, brand spanking new OEM) this has to be a signal or ground issue. Anyone have any suggestions??? Where to start??? Use a multimeter in a specific spot???? Follow a specific wire???? Anything really. I can say that having 1 upstream o2 sensor working is better than neither at all cause (in case somebody doesn’t know) if you try driving the car with both upstream sensors not working (Bank 1 Sensor 1 & Bank 2 Sensor 1) the car will not go past 2000rpm and it was just burble the whole time. So yeah any inputs would be very helpful for me at this point. We all love wiring!!! LOOOOL

[VStar650CL]

See EC-501 for your wiring diagram:
https://www.nicoclub.com/service-manual ... 7%2Fec.pdf
The A/F sensors are on the third page. EC-510 and EC-512 have the sensor pinouts. You can cross reference the ECM pin numbers with the pin descriptions starting on EC-489 to determine the functions of each wire.

[dahomietaz]

i mean that’s a start for me. Thank you. It does help me a little and better understanding. Like which terminal is what number. My terminal 1 is blue. The link you sent me says “L” whatever color that is. i assume it’s the same thing. But my Yellow, White and Red are the same. Forgive me but i’m still a little confused. I scrolled up the section EC-489 but still can’t figure out which wires are signal, ground, and which 2 are heater circuit. Not really worried about heat circuit at the moment cause i’m not getting signal at all. Just trying to figure out ground and signal. I do understand what Volts everything is supposed to be at with ignition on or off or the car while idling. Can you help me out a little more :’( with which 2 terminals are ground and signal? If you can help me figure that out, with process of elimination i can figure out which of the 2 are the heater circuit and ignore those wires for now and fiddle with the other 2 terminals for ground and signal.

[VStar650CL]

L is Blue because B is taken (Black). The General Information section of the FSM always has a few pages about how to read wiring diagrams, including a color chart. See GI-11 here:
https://www.nicoclub.com/service-manual ... 7%2Fgi.pdf

Pins 1-2-3 on the sensor go to 57-61-1 respectively on the ECM, and pin 4 traces back to the fuse in the IPDM on page 1, which you discovered living behind the battery. So referring to the sensor pinout on EC-510, Yellow should be your 12V power. Referring to the ECM pinouts, pin 57 (Blue) is the sensor data which should read 2.2V when running at a normal mixture, pin 61 (Red) is sensor bias which should fluctuate around 1.8V, and pin 1 (White) is the heater output which is PWM'd to ground by the ECM and should read 2.9V~8.8V depending on the sensor temperature. There's no direct ground anyplace on the sensor, both the data and heater circuits are biased/driven by the ECM and not grounded externally.

[dahomietaz]

Thank you!!!!

[VStar650CL]