P0277

P0277 indicates the cyl 6 injector driver circuit is reading high, meaning open circuit, broken winding, or a connector that is not making contact. Cheapest path: unplug the connector at injector 6, swap with a neighboring injector, and recheck; if the fault follows the injector the winding is open. Ohm the suspect winding: PFI saturated injectors should be 11 to 17 ohms, GDI peak-and-hold solenoids 1.5 to 4 ohms; an open winding reads OL (infinite). With the connector plugged in and engine cranking, scope or noid-test the driver line and expect a clean ground pulse at every other crank revolution; pulse width at warm idle is typically 2.5 to 4.5 ms PFI and 0.3 to 0.6 ms GDI. Caveat: a cracked PCB trace inside the PCM injector driver section can set this code intermittently with no harness fault present, especially on flood-damaged ECUs.

Vehicle-specific patterns: 2005 to 2009 Mustang GT 4.6L 3V has a recurring chafe point where the harness crosses the rear of the intake; 2003 to 2007 Ford 6.0L Powerstroke is not applicable here since that uses HEUI, but 2008 to 2010 6.4L Powerstroke does see P0277 from cracked solder on injector pigtail under the valve cover, TSB 09-12-7; 2007 to 2012 Nissan Titan 5.6L VK56DE has a known passenger-bank harness routing that rubs the EGR tube. Estimated repair: $50 to $560.