Nissan Repair Questions? Ask a Mechanic for Answers ASAP
I am sure you know by now that P1273 code refers to a A/F sensor. About all I can do is provide you with a troubleshooting procedure, cause honestly I have never diagnosed a code P1273 on this particular vehicle before. Here is the entire article, that includes some troubleshooting.
Just some quick note though, from reading over it, check for intake leaks, check the fuel pressure, check the grounds, re-tighten that sensor, check the voltage to it, check the sensor for an open/ short.
A/F sensor. I thought you said you replaced 4 O2 sensors.
Unless Nissan is calling o2 sensors A/F sensors. I think maybe they are. I am not familiar with that term though.
I did find P1273 refers to bank 1 sensor 2 lean.
"Clear the engine ECU Self-Learning.
IMPORTANT: If Self-Learning Is Not Cleared:
Here is that entire procedure for self-clearing.
I believe you will need the CONSULT-II tool. Normally anything after 1996 you need a tool, before then you could just disconnect the battery or remove the fuse for the ecm.
I don't actually own a CONSULT-II tool, so I wouldn't know anything about how to use one. if they are too expensive you may want to just go to your closest Nissan dealer and have them do it.