Hows it going, I am in need of some help. So my 09 G37 Coupe got a P2A00 code, Bank 1 Sensor 1 o2 sensor code. I changed the sensor and the code popped right back up again. Is there anything else that could be causing that code the come up again? I've read somewhere that it could also be a bad CAT that can cause that code to come up. Thanks for the help and feedback in advance.

 

I had a similar issue and after the dealer replaced the sensor the code returned. It ended up being an exhaust leak between the cat and the header.

 

I had a P2A03 code which is the pre-cat sensor similar to P2A00 (can't remember which side is which) but you need to check the cat for tiny cracks and ensure the cats are installed/sealed properly against the header/mid-pipe. Replacing your O2 sensor post-cat won't help

Unfortunately this is one of those PITA generic codes to work with but a close inspection is a good start.

A bad cat would cause the post-cat sensors to go off (and trigger a different code) so it SHOULDN'T be your cat

 

I had p2a03 and had a exhaust leak on my aftermarket fast-intentions high flow cats. They are non-resonated versions. The weld cracked so I had it re-welded. P2a03 is driver's side.

 

I don't think the definition of the code is very generic:

P2A00 is defined as:
• The output voltage computed by ECM from the A/F sensor 1 signal is shifts to the lean side for a specified period.

I think some of the cheaper scanners do a poor job with the correct trouble code definitions.
The factory shop manual is the best place to find out the code description.

 

Not sure if I misunderstood but out of curiosity what would the remedy to the lean condition be? upstream O2 sensor replacement or checking for leaks or both? or is more info on the condition needed?

 

Here is what I would do... Before replacing any parts:
• I would look at the total fuel trim (short term + long term) for each bank. They should be fairly close to each other.
• Then I would look at the mass air flow for bank 1 and bank 2. They should also be fairly close.
• Then data log the air/fuel ratio (lambda) for bank 1 and 2 and see how different they are. Again, they should be close.
• I would also data log/graph the rear O2 (narrow band sensor) and see what it is doing.

Here is a nice short video on how the rear O2 sensors works on a G37 or 370z:

The main goal is to figure out is the MAF inaccurate (due to it being dirty) -OR- is the front air/fuel sensor inaccurate (lean bias) -OR- is there an exhaust leak that is allowing in air (O2) into the exhaust and the Air/fuel ratio sensor is just reporting what it sees.

 

Thanks for the explanation!

I swear my learning curve with PID interpretation and diagnosis is 10x longer than dealing with mechanical stuff so this is really helpful

 

Anytime.... You might also like this video that explains all the PIDs on the G37