Just got the Forscan app for our F350 2004. Using it to monitor engine outputs. Checked for DTCs and was surprised to find P0683-60. GPCM comm fault.

It gets cold here in Mn. Truck starts instantly, idle is smooth. No indication that anything is wrong. Glow plug indicator shows on start up. No check engine light.
Glow plug harness was replaced 10k miles ago.

I cleared the code but it came back again. Confused here, I thought this should make the truck hard starting.

Also have a code for the fuel sensor. It makes sense, we get erratic readings that eventually correct themselves. Read of using Techron in the fuel, but am concerned about using it is a diesel. Anyone use it anymore?

Thanks

 

Where in MN are ya? if close we can hook up the IDS

 

In the metro area. But what can IDS diagnose? I understand there are many procedures for check glow plug function, connectivity,etc. but I have no symptoms. Do not want to possibly break something and cause problems where none exist now.

 

From what I have read, you could have one bad glow plug or a faulty connection at the buss bar or glow plug. The truck can still fire with a bad glow plug. Once you start getting more than one, the truck will have issues starting. Again, just from what I have read, not from experience. So with that said, you could ohm out the glow plugs and wiring to see if there's a bad plug or connection.