P0357

P0357 is the cylinder 7 ignition coil primary/secondary circuit fault — this puts you on a V8, V10, or V12 (inline engines stop at 6 in this context). Cylinder 7 location: on Ford Modular V8 it's bank 2 third position (driver side), on GM LS V8 it's bank 2 third position (passenger side), on Chrysler Hemi it's bank 2 third position (passenger side), on BMW V8 (N63/S63) it's bank 2 middle, on Mercedes M156/M157 V8 it's bank 2 middle. Cheapest-first diagnostic: swap the cylinder 7 coil with a known-good front-bank coil that uses the same part number, clear codes, drive cycle. Code follows coil = $35-$150 coil replacement (luxury V8 coils run higher). Code stays at cylinder 7 = trigger wire integrity check (ECM to coil under 0.5 ohms), B+ feed 12.0-12.6V static / 13.5-14.5V running, ground voltage drop under 0.1V. Scope the trigger pulse for clean ECM square-wave. On the deeper bank-2 cylinders of a Ford 5.4L or BMW N63, also inspect for valve-cover gasket oil intrusion into the plug well — oil-soaked boots arc to ground and throw coil-circuit codes that look like coil failure but are actually gasket failure first.

Vehicle-specific patterns: 2004-2010 Ford 5.4L 3V cylinder 7 P0357 — driver bank rear, same TSB 08-7-6 fix, hardest access on Expedition/Navigator. 2005-2013 GM 5.3L/6.0L LS truck cylinder 7 P0357 from D585 failure, swap to D514A; on 6.0L truck applications the rear coils run hotter due to tighter packaging. 2008-2013 BMW N63 4.4L twin-turbo V8 cylinder 7 P0357 from Bosch coil failure — N63 has a service action covering coils, injectors, and valve stem seals as a package; one coil failure usually means the whole set is due. 2007-2011 Mercedes M273 5.5L V8 cylinder 7 P0357 — coils fail in the heat-soaked rear bank position, and the M273 valve cover gasket leaks oil into the plug wells on high-mileage examples. 2005-2010 Chrysler Hemi 5.7L/6.1L cylinder 7 (passenger bank third) P0357 from boot crack — Hemi runs two plugs per cylinder but one coil pair per coil, so a P0357 corresponds to the coil firing cylinder 7's primary plug; check the paired waste-spark cylinder too. 2008-2014 Cadillac CTS-V/Escalade 6.2L LSA/L92 cylinder 7 P0357 — supercharged LSA runs hotter than naturally aspirated; OE coil only. Estimated repair: $35 (one coil) to $4,800+ (BMW N63 service action full package).