If you are looking a non-dealer, try
Walt's Auto Svc
Address:   340 Van Ness Ave # C, Torrance, CA 90501  
Phone: (310) 618-8577
They work on nissan and honda.

Based upon my experience I know what Nissan dealer that has not been honest
with me, and that is Cerritos Nissan.  I bought my 1998 Frontier there and
had it serviced there, but I've had three instances where certain members of
the service department were dishonest with me.  I'll never go back again
(unless they change ownership).

Note:  I should point out; however, that the salesman from whom I bought the
truck, Michael Black, was the most honest car salesman I've ever met.  He is
currently at Douglas Nissan of Huntington Beach, CA.  Incidentally, my
problems with the service dept, started after Michael Black left Cerritos
Nissan.  If I lived closer to Huntington Beach, I would probably have my
truck serviced there.

Does anyone know of an honest Nissan Service Center in Los Angeles?
Preferably near the South Bay or SF Valley area.

I know honesty and car dealers are oxymoron, but what the heck, I thought
I would ask anyway.

tia