P0276

P0276 sets when the PCM sees the cylinder 6 injector control circuit pulled low or shorted to ground when it should be at rest voltage, often because the injector winding is shorted internally or the harness is grounded against a bracket or head. Cheapest diagnostic first: swap injector 6 with another cylinder and clear; if the code migrates you have an internally shorted solenoid. With the connector unplugged, measure winding resistance, which should be 11 to 17 ohms for PFI saturated injectors and 1.5 to 4 ohms for GDI high-pressure solenoids; anything under 10 ohms PFI or under 1 ohm GDI is a shorted coil. Key-on engine-off, both pins of the disconnected injector connector should read battery voltage on the feed and high impedance (open) on the driver until a pulse command; a driver wire that reads 0V key-on with injector disconnected indicates a short to ground in the harness. Caveat: many GDI systems use a separate injector driver module (Ford EcoBoost, GM Gen V, BMW N20/N55) that can fail and mimic a wiring short, so confirm the IDM output before chasing wires.

Vehicle-specific patterns: 2011 to 2014 Ford F-150 3.5L EcoBoost is known for IDM (injector driver module) internal shorts producing cylinder-specific low codes per Ford TSB 14-0180; 2007 to 2013 GM 5.3L/6.0L trucks with active fuel management have harness rub-through at the intake manifold bolt boss on the passenger side; 2005 to 2011 Mercedes M272/M273 V6/V8 with Bosch HDEV-1 GDI injectors suffer cracked solenoid windings around 80k miles. Estimated repair: $45 to $720.