"On Board Computers" - Are there 2 OBCs? How can a problem with either one be diagnosed?

Was this entire diagnosis and repair procedure performed at an actual auto repair facility ?

Yes, and the repair shop is listed w/ 5 stars & certified here @ RepairPal.com. It seemed a quick diagnostic scan (of generic computer?) which showed only the P0443 emissions trouble code. I don't believe any further inspection was done, but purge solenoid valve replacement was recommended/done.

Perhaps there is another - totally different failure this time. I’d return to same repair facility for re-scan. Good luck!

The repair shop apparently has limited diagnostic tool (which had only showed the one problem code) -- told they cannot check the "manufacturer" OBC, only the generic portion. I called them to report check engine light was back on, after $400 solenoid purge valve replacement! I was told to contact a Nissan shop, presumably to get a more sophisticated diagnostic scan? I've tried to contact the nearest Nissan dealer but haven't heard back yet.

Go by Advance Auto / AutoZone get the codes read - post all code numbers. I’ll see what I can do from here.

I phoned AutoZone, explained the (general diagnosis P0443) problem, but they apparently don't have any diagnostic equipment more specialized than my repair shop. It was suggested that a smog station (test) might provide some further info about the "emissions" problem.

What I need to know is all codes that are presently stored.. Additional codes that are new to the system. Only way to discover that is having codes read again Not really concerned with historical codes at this point.

I would like to know more codes also! If I return to the repair shop for a repeat scan, I anticipate the result will be the same, i.e. non-specific "emissions" problem. Are there any visual inspections that might yield info? Although the shop would charge $__ (?) for labor.

Zone or Advance will read the codes for free and give you a printout. I need ALL presently stored codes.

AutoZone has no special diagnostic equipment beyond what my repair shop has (see earlier reply). Phoned Advance Auto in SF, told that a diagnostic would incur hourly labor charge (not free), and I didn't like the man I spoke with, heavy accent and sounded like he just wanted $$.

Now seems my best option is try to make appt. w/ Nissan dealership in Petaluma CA. Nissan USA told me that a dealership should have the proper advanced diagnostic equipment to determine OBC codes.