P0354

P0354 is the cylinder 4 ignition coil primary/secondary circuit fault. Cylinder 4 location: on inline-4 engines cylinder 4 is the flywheel-end cylinder (opposite the timing belt/chain), on Ford Modular V8 it's the rear cylinder of bank 1 (passenger side), on GM LS V8 it's the rear cylinder of bank 1 (driver side), on Chrysler Hemi it's bank 1 rear, on BMW inline-6 it's the middle of the engine block, on Toyota 2GR V6 it's the rear bank middle. Cheapest-first diagnostic: same pattern as P0351-P0353 — swap the cylinder 4 coil with a known-good neighbor, clear codes, drive cycle, watch where the code goes. If the code moves with the coil, $35-$120 fix. If P0354 stays at cylinder 4, the issue is on the cylinder-4 side: trigger wire integrity (ECM to coil under 0.5 ohms), B+ feed at the connector (12.0-12.6V static, 13.5-14.5V running), ground integrity (under 0.1V drop coil-ground-to-battery-negative under load). Scope the trigger pulse — clean 3-6ms dwell square wave at idle, RPM-following. On rear-bank/rear-cylinder positions like this one, heat soak is the cumulative killer — coils that test fine cold and fail hot are the rule, not the exception, on Ford and Toyota V8s.

Vehicle-specific patterns: 2004-2010 Ford 5.4L 3V cylinder 4 P0354 is the rear-passenger cylinder under the cowl — it's the hardest plug/coil to physically reach (intake manifold removal recommended on Expedition/Navigator) and the most heat-soaked, so it's often the first to fail in a set. TSB 08-7-6 still applies. 2005-2014 Toyota Tundra/Sequoia 5.7L 3UR-FE cylinder 4 P0354 — Denso COPs are durable but the rear-bank cylinder 4 position cooks under sustained towing; OE Denso replacement only. 2005-2013 GM 5.3L LS truck cylinder 4 P0354 from D585 failure, D514A is the updated part. 2007-2014 Nissan VQ35 cylinder 4 P0354 from rear-bank coil and valve cover gasket — VQ35 rear-bank service requires partial intake removal. 2003-2010 Chrysler 5.7L Hemi cylinder 4 (passenger bank rear) P0354 from worn coil boots cracking under exhaust manifold heat — Hemi coils sit between two exhaust manifolds and run hot. 2002-2008 Ford Ranger/Mustang 4.0L SOHC V6 cylinder 4 P0354 from cracked coil-on-plug body and chafed harness over the rear bank. Estimated repair: $35 (one coil) to $600 (full coil set + intake gaskets on a Tundra).