P0294

P0294 is V12-only and sets when the PCM detects the cylinder 12 injector circuit pulled low or shorted, where cyl 12 is typically the rearmost cylinder on bank 2. Cheapest first: swap injector 12 with another cylinder on the same bank and clear codes. GDI solenoid windings on Mercedes M275/M279, BMW N74, Lamborghini L539, and modern Ferrari V12 should ohm 1.5 to 4 ohms cold; under 1 ohm indicates a shorted winding. Key-on engine-off, driver-side pin should be open to ground with injector unplugged; 0 ohms to chassis ground indicates a harness short. Pulse width at warm idle on these engines is typically 0.3 to 0.7 ms GDI, with cold-start enrichment widening to 1.2 to 1.8 ms briefly. Caveat: on Mercedes M275/M279 cylinder 12 access requires removing the rear intake plenum on most chassis (W221, W216, R230), so spend the time on connector pin-drag testing and IDM swap diagnostics before committing to teardown; the labor delta between a 10-minute IDM swap and an injector R&M is 4 to 6 hours.

Vehicle-specific patterns: 2003 to 2014 Mercedes-Benz M275/M279 V12 (S600, SL600, CL600, S65 AMG) has documented HDEV-series injector winding failures and IDM channel-specific faults that present as cylinder 11/12 codes first; 2009 to 2015 BMW 760i/760Li N74 V12 has TSB-documented injector driver module replacement procedures (BMW SI B12 09 13); 2002 to 2010 Ferrari 612 Scaglietti and 599 GTB F133 V12 use port-injected solenoids that fail at the connector seal allowing moisture intrusion. Estimated repair: $200 to $2,800.