Failure mode - Ford 6.7L Power Stroke Diesel (Scorpion)

Glow plug wear and cold-start faults, plus an isolated 2011-2013 tip-separation defect

Reliability tier: verified - verify before ordering, see /disclosure/

Symptoms

routine wear: extended cranking and rough running on cold mornings, growing worse as more plugs fail; white/gray smoke at cold start that clears as the engine warms
glow-plug circuit codes P0671-P0678 (per-cylinder) or P064C (control module)
a 'wait to start' lamp that no longer illuminates (points at the control module/wiring, not the plugs themselves)
SERIOUS defect, 2011-2013 engines specifically: a broken-off glow-plug tip travels through the cylinder, hammering the piston, valves, and turbocharger - a compression-test-worthy finding on any used 2011-2013 truck with unknown history

Compare with the other causes of the same sign on this engine: hard start, long crank or no-start (4 causes) · white smoke from the exhaust (3 causes) · misfire, rough idle, hesitation or surging (5 causes)

Root cause

Below roughly 50F the 6.7L leans on its eight glow plugs plus an intake-air-heating strategy to light off cleanly. Routine wear is ordinary component aging. Separately and more seriously, a number of very early 6.7L engines (2011-2013) suffered glow-plug TIP SEPARATION - the heated tip breaking off inside the cylinder and causing mechanical damage downstream. Ford addressed the defect with revised plugs early in production; our editorial notes independently corroborates 'isolated early-production glow-plug tip breakage, mainly chassis-cab reports' from a separate source (Wikipedia's engine article), giving this specific defect two-independent-source backing distinct from the routine-wear claim. Poor cold starts are also frequently a battery-condition issue rather than a glow-plug one - two aging batteries that crank slowly rob the engine of the compression speed needed to light off, 'a winter no-start wearing a glow-plug costume' per the vendor source.

Diagnosis

individual plugs test with a multimeter: ~1-2 ohms to ground on a healthy plug, open circuit confirms failure
verify control-module voltage delivery to each plug during the pre-glow cycle before condemning plugs
on a used 2011-2013 truck with unknown service history, treat a broken-plug-tip suspicion as a borescope-inspection and compression-test item before driving it further, not a wait-and-see

Fixes

replace glow plugs in complete sets on a high-mileage engine, using a quality torque wrench (routine wear) ()

6.7L Power Stroke Glow Plug

replace the glow-plug control module when module-level codes point there rather than an individual plug ()

glow-plug-control-module - more than one option: Glow Plug Control Module, 2011 only, Glow Plug Control Module (2017-2019), Glow Plug Control Module (gen1), Glow Plug Control Module (gen1) (current service PN BC3Z-12B533-C), Glow Plug Control Module (gen2)

on a confirmed tip-separation event: this is engine-internal damage (piston/valve/turbo), not a plug swap - inspect and repair the downstream damage, not just the plug ()

Prevalence

occasional