I read a lot on it, P1320 with no misfire. I was not about to take it to the shop or dealer to have all coils and spark plugs replaced. That would have been over $1000 bucks. So I read on, researched anything and everything I could find. Ordered the coils but while I waited for them to arrive, I did the following and it made my day.
I took the coils and spark plugs out. All the spark plugs looked great, they were relatively new and NGK OEM. The coils were mixed, 2 appeared to have been recently replaced with aftermarket ones. Brands: 1 by autopart, 3 original Nissan OEM, and 2 with no brands that I could read. I looked further into the coils and removed the long boot that connects from coil to spark plug. Took out the long spring and looked into the contact section on the coil and what do you know? Found the smoking gun. Some of the OEM coils had evidence of arcking, smoke build up on spring contact section.
My solution cost me zero dollars. Cleaned contact areas, applied dielectric grease which I had already, stretched out the springs which had lost tension and put them back on. SES light was gone for good, well for now. Lol.
My recommendations: Anytime the SES comes on with P1320 or plugs are replaced, check the coils for evidence of arcking, coil springs for tension (stretch them out if needed) and apply some dielectric grease to contact sections.
I discovered and believe this to be the problem in this case. The original OEM (old) coils had very loose springs, thus they would make poor contact, cousing the arcking and random misfire. Also poor design on contact section with the spring, a flat surface. One good coil had a cup-like design that held the spring in place, that was good, another had a long nipple-like design the went inside the spring and held it in place, that was great. I assume that the springs lost tension over time due to heating and cooling, and the first ones to fail had the flat contact section. The P1320 with no misfire, no coil pinpointed or identified, would be very random, maybe on a cold day, after hitting a bump or pothole on the road would triggar the SES light. The coil is good but the spring is loosing tension. Thats why some owners see this light come on before the coil totaly goes out and misfires. Good luck folks!
