P0285

P0285 indicates a low-voltage / short condition on the cylinder 9 injector circuit, which only appears on V10 and V12 engines. Cheapest first: swap injector 9 with a known-good neighbor and recheck; PFI windings should ohm 11 to 17, and on V10s like the Ford 6.8L Triton this is a port-injected saturated solenoid, so under-10-ohm readings indicate a shorted coil. With the injector unplugged and key on, the driver pin should be open to ground; any continuity to chassis indicates a harness short to ground. Pulse width on a warm-idle Ford 6.8L is typically 3 to 4 ms; on a BMW S85 V10 the GDI-like sequential setup runs 2 to 3 ms at idle. Caveat: the Ford 6.8L 2V/3V Triton has spark-plug-blowout history on cylinder 9 because that head is shared with the 5.4L V8 pattern; a blown plug can damage the injector harness running alongside the COP, so always inspect for plug-thread damage signatures before condemning electrical parts.

Vehicle-specific patterns: 1997 to 2010 Ford E-Series and Super Duty 6.8L V10 Triton is the dominant population for this code and most failures trace to harness chafe at the right-rear valve cover or to spark-plug-blowout collateral damage on cylinder 9; 2006 to 2010 BMW M5/M6 S85 V10 has documented bank-2 injector driver weakness in the DME; 2003 to 2010 Dodge Viper 8.3L V10 has cracked injector connectors from underhood heat. Estimated repair: $55 to $980.