Hi!
Longtime Nissan owner here.
Just got a 2006 X w/180K mi a couple weeks ago.
It had the dreaded PO300 (multiple cylinder misfire) when I bought it cheap.
I have cleaned all the grounds, replaced the battery neg cable, all new plugs (NGK), coils, MAF, ECM relay, fuel injectors, knock sensors, 02 sensors, LIM and upper gaskets, cleaned the TB, and probably something else I forgot.
That cleared up the PO300 and occasional knock sensor codes, now I am stuck with the PO305 and occasional PO132 High volt (rich) bank 1 (which leads me to assume the brand new injector is OK since I hate taking off that manifold). I swapped in 3 different coils and spark plugs and all the same PO305.
I have tested the coil harness ground and it's good, and has 12V+. I can't test the violet signal wire for signal yet since I don't have a Hz meter or oscilloscope, but it seems to have about .5 volt (should have 5v?).
Fuel pressure is 51# .
All the grounds were pretty ugly, the battery neg cable looked like it got pretty hot.
Looking at a new ECM?
Any ideas?
Thanks