Ford F-250 7.3 V8 Diesel Code: P0672

Could be your GPCM. Although you could try switching your new GP's to see if it changes anything?

DIAGNOSTIC PROCEDURE
The GPCM supplies power to the glow plugs through solid state drivers and performs diagnostics internally to detect and report system failures. The Powertrain Control Module (PCM) still controls glow plug on-time through a control circuit between the two modules. On-time is a function of engine oil temperature, barometric pressure, and battery voltage. This is the same as the previous system.

There are two circuits connecting the PCM and the GPCM. PCM Pin 101 is still used as the control circuit which activates the GPCM to enable glow plugs. PCM Pin 8 is used as the serial communication circuit which is used for the GPCM to report failures to the PCM. The PCM monitors these circuits for failures. The GPCM internally performs diagnostics for individual glow plug/glow plug circuit failures. When a failure is detected, the GPCM will transmit that failure to the PCM over the communication circuit. If a fault is detected, it will be stored in PCM continuous memory. New fault codes have been added and descriptions are as follows:

P0670 - Glow plug (GP) control circuit malfunction
P0671 - Glow plug #1 circuit failure (circuit/GP)
P0672 - Glow plug #2 circuit failure (circuit/GP)
P0673 - Glow plug #3 circuit failure (circuit/GP)
P0674 - Glow plug #4 circuit failure (circuit/GP)
P0675 - Glow plug #5 circuit failure (circuit/GP)
P0676 - Glow plug #6 circuit failure (circuit/GP)
P0677 - Glow plug #7 circuit failure (circuit/GP)
P0678 - Glow plug #8 circuit failure (circuit/GP)
P0683 - Glow plug diagnostic signal communication fault
When servicing this system for fault codes, carefully inspect all connections for damaged or pushed out pins and fully engaged connectors. The green engine harness connector must be connected to the green glow plug monitor connector and the black engine harness connector must be connected to the black glow plug monitor connector. After any repair or removal of the GPCM components, it is very important to re-run the KOER Glow Plug Monitor self test to verify no system faults are present before releasing the vehicle. For diagnostic procedures, refer to the new pinpoint test for the GPCM system (Figures 1-6).