Troubleshooting P1668

[GreenF350]

I have no hard codes set and the truck runs fine, however if I run a buzz test on the truck it will return a p1668. Now, I know that this codes means there is a communication problem between the IDM and the PCM and I have found a few mentions of chasing grounds and wires in the harness between the two. WHat i don't have is any information as to exactly what wires, colors, locations, anything to get me started. Does anyone have any information where to start on this one? I am a pretty capable mechanic but I think some better resources would be helpful on this one, especially if it is just a bad connection and not a broken wire or something.

Also, does anyone happen to know if this code specifically identifies what the communication problem is or what "communication" it is looking for. Not so much for troubleshooting (although it may help) but because I am wondering if it could cause minor problems and I'm just one of those people that like to know how things work.

Thanks guys, the .org hardly ever fails me.

-Aaron

[dray8165]

Here's an instructional on how to test the wiring:

http://www.gbreman.com/docs/techbull...eplacement.pdf

Here's a thread from another site concerning the exact same thing:

http://www.thedieselstop.com/forums/...-error-185328/

Apparently this is common after doing the buzz test.

[GreenF350]

Thanks. Looks like a good place to start. I got the p1668 code after doing a buzz test with the Terminator Engineering Scan Gauge. I'm not sure what to think though because I ran down to a shop where I know a few guys and borrowed their Snap-On scan tool and ran the same test a few times and didn't get ANY codes. I wonder if the gauge is accurate with it's test results since the truck runs fine. I might have to pull the gauge out and try it on one of my friends trucks.
-Aaron