[07Versa6MT]

Probably just used a spark plug non-fouler to take it out of the exhaust stream so it reads lean all the time so doesn't set the cat-efficiency or O2 CEL's.

What are you talking about when you say "you never know what else might pop up other than the O2 sensor"?? What does this mean?

 

[07Versa6MT]

Your car ideally won't set codes during the first few years of ownership, and shouldn't if you keep up on maintenance and inspect things frequently. I have an 07 1.8 with 338 000KM on all original sensors and still no DTC's, not even any pending codes. I don't know how the supply chain is for current model years, and if the suppliers for stuff like sensors and modules has improved design and improved quality control or if it's reduced, so i can't speak for how current MY's will fare as they age, but if recent history is any indication, quality and reliability should only have increased.

My generation Versa's had alot of problems with various modules and sensors.