Diagnostic Aids
WARNING: This page is about a different variant/trim than selected.
This test is for models with Federal emissions only. Perform this test when directed by QUICK TEST. This test is only intended to diagnose the following components and circuits:
- Glow Plug Relay
- Harness Circuits (GP/RELAY Coil)
- PCM
NOTE:
WAIT TO START indicator ON time is independent from glow plug relay ON time (1-10 seconds).
- Output Functions
Glow plug relay controls current flow to glow plugs. Glow plug relay ON time is controlled by PCM and is a function of engine oil temperature, barometric pressure and battery voltage. Glow plug ON time normally varies between 10-120 seconds. Glow plug ON time is dependent on oil temperature and altitude. Glow plug relay comes on between 1-120 seconds and does not come on at all if oil temperature is above 86°F (30°C) for Econoline, or 131°F (55°C) for Excursion and F250-750. Using scan tool, you can run OUTPUT STATE SELF-TEST, which will cycle glow plug relay on for 5 seconds, the first time only, that accelerator pedal is pressed. OUTPUT STATE SELF-TEST does not set DTCs. - Detection & Management
An open or shorted to ground glow plug relay or WAIT TO START indicator circuit can be detected during KOEO ON-DEMAND SELF-TEST. On all vehicles with Federal emissions, glow plug and glow plug harness concerns cannot be detected by PCM.