Key On Engine Running (KOER) Glow Plug Monitoring Self-Test
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2006 Ford RV Cutaway, 2006 Ford Pickup, 2006 Ford F550 Super Duty, 2006 Ford F450 Super Duty, and 2006 Ford Econoline. However, it is still accessible from the selected car via links, so may be relevant.
The KOER glow plug monitoring self-test is an on-demand functional test of the glow plug system carried out with the engine running and the A/C off. Battery voltage must be maintained at 10-14 volts during this test. If necessary, apply the accelerator pedal to increase voltage to the specified level. The PCM activates the glow plug control module (GPCM) and monitors the glow plug circuits. A fault must be present at the time of testing for the test to detect a fault. DTCs are sent to the PCM on the diagnostic line and then output to the diagnostic tool.