Not a typical P0678 Glow Plug Code

[cub124]

I've been having trouble with a P0678 code. Changed the glow plug (drivers rear, #8) but the code continued to come back. So I traced the wire by checking resistance and checking for a short. Nothing so the GPCM was replaced & reprogrammed. However the code still persists. Went back & checked the wiring again but no issues of interest and also tested all glow plugs with resistance to ground from the main GPCM wire harness. They were all between 1.3-1.8 ohms. I even tried the test light test and I also changed the #8 glow plug out again along with terminal cleaning.
Still stumped.
Anyone have a similar issue before or know of any likely places the #8 glow plug harness could be shorting out at?

The truck is 2006 GMC 3500 Cab & Chassis LBZ with egr delete & EFI (the grid heater was removed with the egr delete) Although it should have its own code not related to #8 GP.

 

[j johnson]

are you using acdelcos for the glow plugs...i say that because ive read were anything other than ac wont last long in the duramax engines thats been my experience besides thats what came with the truck...scott

 

[RI Chevy Silveradoman]

Just checking, but did you clear the code prior to restarting the engine? And I assume that you are using EFI Live to conduct this test?
I haven't heard of any issues like this with any 2006 LLY/LBZ trucks.