I have a 2008 Infiniti G35 with 96,000 miles. No modifications at all. I am unable to pass smog and in serious trouble as my car as I probably shouldn't be driving as registration expired. I am in CA and smog checks are strict.

Had a p2a00 code referring to bank 1 sensor 1 and had it replaced by a local shop. Light came back on. Went to dealer and they ran a diagnostic with Consult III showing freeze frame data displaying the voltage of my oxygen sensors. They claim that this squiggly line for B1 means that I need a new catalytic converter.



I am assuming it's the fluctuation in voltage between the front and back sensors which may indicate a bad cat? I am a bit skeptical because I asked another shop for a second opinion and he says that the front sensors are BEFORE the cat, so they never tested the cat. I also never had the code for a bad cat which is P0430 which shows that it's below threshold.... So I am not sure that I believe the dealer... Also, aren't they supposed to do a temp and air pressure test to check the cat? And how do they know it's bad? What if there is a leak or a clog instead?

I also googled around and found that apparently a lot of people on this forum are having troubles with this particular code with this particular car... so it's something that affects this vehicle for some reason..... So how do I fix this?

From what I gather reading:

check spark plugs?
Plug and unplug battery to reset ECU?
Possibly catalytic converter needs to be welded?
Anything else I am missing?

Is the dealer blatantly lying when they say I need a new cat? I have it in writing here below. Also, please, what should I do in order to clear this damn code so I can pass smog? I am getting really frustrated dealing with this. Thank you for your help.

 

For the part I used a Denso... is it possible that since one sensor is Denso and the rest are OEM that it's tripping up the system?

Does anyone know if the dealer is giving me the correct info that i need a new cat based on the graph above?

I googled this issue and most people don't need to replace their cat with a p2a00.... in many cases it was a leak or a crack in the cat. If the cat failed there is usually a specific code for that which is p0420 cat below threshhold.

I just need to know if i truly need my cat replaced or not as it's going to cost me $1400.

Already spent over $500 trying to fix this (2 dealer diagnostics, replacing sensor and failed smog tests).

 

I wanted to post my experience with this code and findings. This is on my 2006 G35 Coupe that ive had since new, miles now are at 195,000 miles and on the original O2 sensors. Most of its life, have fueled up with premium fuel.

Here is the checklist on what I replaced that didn’t work on the solution, still got a check engine light after resetting ECU after chasing it for a solid 4 months.

• upstream sensor with an OEM part
• Replaced downstream oxygen sensor with an AutoZone brand/Walker brand
• fuel pressure regulator
• Airflow sensor
• Smoke tested the intake and hoses in engine bay
• Air leak tested the exhaust for signs at the catalictic converter and exhaust manifold
• OEM Spark Plugs

the fix ended up being, having an inferior downstream O2 sensor that I got from AutoZone. So I replaced it with an NGK brand instead from Amazon https://amzn.to/3GStdHW, from this link

Hope this helps anyone coming up with hiccups. Yes, the code says to replace the upstream sensor as a solution but in the end, the downstream readings were incorrect all along by a faulty replacement.

 

It's become quite apparent on the forum over the years that these cars are very sensitive about aftermarket sensors. Everyone's best bet is to use only OEM or Hitachi sensors (Hitachi is the OEM manufacturer). All others are at your own risk.

 

Wanted to toss my experience for fixing this, I had a tiny pinhole right near the O2 sensor. It was where the bracket attached, rusted off over time and eventually there was a spot for air to get through.

Used some putty to fill it and I have had no codes since. Not a great solution but enough till I can rip the cats and get it properly welded.