I had an e30 on one and replaced the alternator and ecm relays and battery. She ran fine after but the code kept coming back after clearing it every 2 key cycles. I ended up leaving it and low and behold it cleared after an unknown amount of time. I always have a negative look at things in general which makes me draw this conclusion: If I had access to the correct diagnostic software the code would have been able to be cleared the first time.
Also I have some which run slightly rougher than others, the drivers don't notice anything different but i do. No codes fuel system clean fresh tune up parts, I believe there is a calibration for the air fuel ratio which probaly needs to be done but I can't get any answer except cat laptop is required. I don't have any nissan or cat friends and want to know if there is some way i can do this.