I have a 2004 3500 truck, VIN code 2, LLY, that was towed in for no start. Only code it is setting is U0105, fuel injection control module not communicating. Primer pump pumps up tight. No exhaust smoke when cranking. Is there a data stream item you can watch to see if injectors are firing? Checked wiring by alternator bracket and at engine disconnects. Look good. Checked for 12v at module, good. Checked grounds below module on block, good. Someone has run a replacement harness to fuel rail pressure sensor. No idea why. Truck was bought at an auction, so I have not history. Any ideas. Thanks

 

no smoke at crank means injectors are not firing

 

I know the RPM requirement, fuel rail pressure requirement. Does anyone know what the injector pulse width signal is required? The GM manuals say that if a data bus signal is missing, it substitutes a set value.