Hey, i'm having an issue with a 6.6 in a 2007 C4500. The engine is an LMM ( i think...the 8th digit is 9). I'm getting a P0480 DTC. The cooling fan is not kicking in.

The engine temp only goes to 170 when idling...on the interstate though, it gets hot and shuts down the engine. Not sure what the engine temp when it shuts down, but it doesn't appear to be over 220 by the guage. Everything appears to be working as designed according to the tech II, except for the operating temp at idle.

The radiator, water pump, fan (and clutch), coolant sensor, egr valve, egr cooler, condensor, accumulator, orifice tube, and ac lines have all been replaced.

The 5v circuit is good according to the tech II and I'm assuming the relay is good as I can command the fan to 100% manually and you can hear it roar.

Has anybody seen anything like this?