This 400,000-mile LLY Duramax pulled into the shop with a miss. The owner, who'd owned LB7-powered GM's in the past, feared it was a bad injector. However, less than an hour's worth of troubleshooting confirmed the real problem: an open circuit in the engine's wiring harness. A wire on the driver side of the engine had rubbed off its insulation and was grounding out on the bracket below it, causing an electronic fault in the number 7 injector output circuit (code P1241). The exposed wire was simply re-wrapped, as well as the entire harness, and the problem was solved quickly, and on the cheap.
Beat on since day one, this LLY farm truck is proof that the Duramax can last. The only major repair it's needed in its 390,000 mile history was a water pump, which all of the Big Three typically need somewhere between 100,000 and 200,000 miles.