P1320

P1320 is Nissan-specific: the ECM detected an abnormal primary-side signal from the ignition module/igniter that sits between the ECM and the coil-on-plug packs. On VQ35/VQ37 and earlier VG/KA platforms, the ECM sends a low-voltage trigger and expects a 0V-to-12V square wave back from the igniter primary as confirmation; missing or distorted pulses set P1320. Cheapest-first ladder: pull each coil, inspect the connector for green corrosion and bent pins, then scope the primary trigger line at the coil connector during cranking (you want a clean 0-12V square wave at firing frequency — flatlined or noisy = igniter or coil dead). Swap one suspect coil with a known-good adjacent cylinder, clear the code, and see if the fault moves. Check power and ground at the coil too: battery voltage on the feed during KOEO and clean ground through the harness back to the ECM. Don't replace the ECM until you've ruled out every coil and the igniter circuit — Nissan ECMs are $600-$1,500 and almost never the actual fault on a P1320; the cause is a $120 coil-on-plug 90% of the time.

Vehicle-specific patterns: 2002-2006 Nissan Altima/Maxima with the VQ35DE is the textbook P1320 ticket — the OEM Hitachi coils crack internally around 80-120K miles and throw P1320 plus a cylinder-specific misfire (P0301-P0306) together; replace as a set of six, not one at a time, because the rest are usually 70% of the way to failure. 2005-2012 Pathfinder/Frontier/Xterra with the VQ40DE shows the same pattern but adds connector corrosion from engine-bay heat soak — clean and dielectric-grease every coil connector during the job. 2002-2006 Sentra/SE-R with the QR25DE 2.5L throws P1320 from coil failure plus the well-known timing-chain stretch retarding cam timing, which masks itself as an ignition fault. 1999-2004 Frontier/Xterra with the VG33E 3.3L V6 throws P1320 from the original distributor-style ignition module degrading — usually a full distributor replacement rather than just the module. Estimated repair: $120 (single coil DIY) to $900 (full coil set + plugs on a VQ35).