P0279

P0279 means the cylinder 7 injector circuit is reading low, which the PCM interprets as a short to ground or an internally shorted injector solenoid. Start cheap by pulling injector 7 and swapping with a known-good unit; if the code follows the injector it is internally shorted. Bench-ohm both injectors: PFI saturated should be 11 to 17 ohms cold, GDI solenoid 1.5 to 4 ohms cold; a shorted PFI winding typically reads 4 to 9 ohms, and a shorted GDI winding reads under 1 ohm. With the harness side disconnected and key on, the driver pin should read open (high impedance) to ground; a driver pin reading 0 to 0.5 ohms to chassis ground is a harness short. Caveat: on Chrysler MDS-equipped 5.7L Hemi engines, cylinder 7 is one of the deactivated cylinders, so the injector sees longer dwell off-times and any marginal winding will fail there first, masking a fleet-wide injector quality issue.

Vehicle-specific patterns: 2005 to 2010 Dodge Ram 1500 5.7L Hemi commonly throws P0279 from cracked injector solenoid windings on the deactivating cylinders, Mopar TSB 18-040-07; 2007 to 2013 Chevrolet Silverado 5.3L AFM trucks see the same pattern on cylinder 7 due to active fuel management dwell stress; 2005 to 2008 Ford Mustang GT 4.6L 3V has harness chafe at the rear bank near the firewall heater pipe. Estimated repair: $55 to $510.