2004 G35 Coupe with 67K miles
I am in California and I am trying to pass smog test. Here is what's happening:
Got a P0037 and P0057 DTC and changed both down stream Heated O2 sensors. Completed drive cycle to reset the ECU and turned off CEL. Took it to get smogged and it states Catalyst and Heated O2 sensor not ready. (everything else is good)
Pulled DTC and it shows a P0057 pending and N/A as a fault? CEL comes on after 18 miles of driving.
I have checked the wiring and the O2 sensor fuse and all are good. Last thing should be the ECU so I am posting here to see if anyone who is smarter than I am on the G35 can help me out.
A few suggestions from other people........Cat problem. shouldn't be because DTC is an electrical problem and you won't know a bad CAT unless it fails emissions.
Upstream O2 sensors are bad causing Cat not ready but no code and the P0057 DTC?

lots of View but no one able to assist. Is this an unheard of problem with the G35?

What brand of sensors did you buy?

I bought Bosch plug and play. Bank 1 works great and got rid of the P0037 and just to make sure I swapped out Bank 2 twice and still get the P0057. Computer shows Oxygen sensors available but not ready

The code means that there is a problem with the heater element circuit of the heated oxygen sensor. Water getting inside the heated oxygen sensor connector can caused the heated oxygen sensor fuse to blow, which is a very common problem for this type codes. Before replacing the sensor, check for the condition of the heated oxygen sensor fuse and connectors.

So I have checked out all the wiring and the fuse is in tact, even swapped it with known good cig lighter fuse. I know what the code means just needed to know if there was anything I missed or haven't checked before I replace my ECU. If the sensor and wiring are good (All sensors show available but not ready on my computer ODBII program)

What are you using to read your OBD-II Diagnostics?

I am using ODBwiz program with a ODBlink usb to my laptop shows PID and everything. The O2 sensor show available but not ready. along with O2 sensor heater and catalyst. Dealer say its not likely a Cat because of the mileage. The P0057 DTC shows pending ECU 10 powertrain. CEL stays off when the DTC is pending and comes on eventually but DTC still shows. The ODB program will show a available of All O2 sensors Bank 1 and 2 Upstream and Bank 1 and 2 Downstream but no data is available due to incomplete self test.

I have OBDLink as well (The MX version) also on an '04. If there's anything you want me to check and give back some readings on what normal operating values are for this setup, let me know. I use my phone to read it though, not a laptop. I have a few different phone apps but find the OEM OBDLink software to be surprisingly good.

Well if I could get the PID for the O2 sensor volts and other read outs that would help, I have rough estimates but would like the actual values.
Kinda reaching the end of my rope on this one now

After talking to the Stealership they tell me that since I can clear the code and have no DTC's for a while indicates to him it is more likely an ECU/ECM problem. Since I have replaced the O2 sensor with an infiniti OEM and still get the code. It shows Pending for Power train ECU10 before it turns back on the CEL. It varies on how long it takes for the DTC to show back up. They say if it were a short in wiring it would be constant because it would fail self check so in my case the ECU is simply not turning on the heater element for the Bank 2 rear sensor and that could be the cause of all the other incomplete checks which causes a "not ready" state.

Thoughts?

I just went out and tested it on my car. I'm not sure how to check what the associated PID is for each preprogrammed dial/gauge in Torque or OBDLink, but I assume the ones for our car are just the standard O2 sensor bank 1 & bank 2 sensor 1 voltage PIDs since I was able to get data for both by using the built in displays for those two.

My O2 sensor bank 1 sensor 1 voltage seems to mostly hover around .29 with the lowest value it hits being about .2 and the highest being .8.

My O2 sensor bank 2 sensor 1 voltage seems to mostly hover around .63 with the lowest value it hits being about .4 and the highest being 1.3

Let me know if you need anything else specifically.

Ok so I got the car on a lift and inspected every wire in the system. P0057 is definitely an electrical problem.
Bingo I found a cut wire under the sheathing on the Bank 2 sensor 2 wire bundle. There was an inconspicuous scratch mark on the sheathing and unless I pulled it back I would have never seen it. I can understand why so many people missed it and why I got the car for such a cheap price.
Passed smog and inspection same day after repair of wire. All systems green.
Always trust your gutt

Nice! Good job. I bet you feel like a ton of weight has just been liftedoff your back.

Sorry to reply uber late to this forum.

I am having a similar issue with my g35 03 130k. The Code is p0057 and i have checked all wiring, fuses and replaced both dowstream sensors. I have put on nee NTk sensors since they are the oem brand. My mechanic says i might need new catalyc converters but he us not sure it will fix the problem. The dealership says its an electrical problem and most likely the ECM. Any thoughts or ideas?