P0305

P0305 means cylinder 5 is misfiring, which only exists on engines with 5 or more cylinders — so you're looking at a 5-cylinder inline (Audi/VW 2.5L, Volvo white-block, GM Atlas), an inline-6, a V6, a V8, or a V10. The diagnostic flow is the standard misfire drill (plug read, coil swap, plug swap, compression, injector balance), but cylinder identification matters more than on a 4-cylinder. On a Ford 5.4L 3-valve V8, cylinder 5 is the front-most cylinder on the left (driver's) bank. On a GM LS-series V8, cylinder 5 is the second cylinder from the front on the left (driver's) bank. On a Chrysler 5.7L Hemi, cylinder 5 is the front-most cylinder on the left bank. On a transverse Chrysler 3.6L Pentastar V6, cylinder 5 is the middle cylinder of the right bank. Get the FSM cylinder map before you start swapping or you'll burn 30 minutes on the wrong COP coil.

Vehicle-specific patterns: 2004-2008 Ford F-150/Expedition with the 5.4L 3V Triton is the king of P0305 — the 3-valve cylinder heads have a well-documented stuck-spark-plug issue (carbon welds the plug to the head) and the cam-phasers fail and rattle, both of which manifest as misfires on the left-bank cylinders 5/6/7/8. 2005-2010 Volvo XC90/S60 with the 2.5T inline-5 commonly throws P0305 from a failed ETM (electronic throttle module) creating uneven air distribution; the rear cylinders see it first. 2003-2009 Audi/VW 2.0T (BPY, BWT) and the 2.5L five-cylinder (Jetta, Beetle) frequently throws P0305 from coil-pack failures that hit one cylinder at a time — Audi/VW typically warranty-replaced the whole set. Estimated repair: $40 (single coil) to $2,200+ (cam phasers on the 5.4L 3V).