FYI: This is how the glow plug logic works:
Please note, the Glow Plug light on the dash
only illuminates for 1 second until the coolant temperature drops to -10C at which point the light on the dash illuminates for a full 10 seconds according to the control chart ...
Even though you will only see the light on the dash illuminate for 1 second
(and you may miss it if you are not looking at it) the ECM continues to heat the glow plugs for up to 21 seconds after the dash light has only *blinked depending on the coolant temperature!
*Seems like stupid logic by FCDJ to me, why not just illuminate the dash light for the entire period of time the glow plug is being heated? Duh, a no brainer, STUPID!!!
So, based on all of this; in cold weather, leave the ignition switch in the ON position for the entire period of time as listed before trying to start the engine and it may alleviate some of your cold start issues...
Pre- is heating time prior to engaging the starter motor, and Post- is heating time after the engine starts!
Any questions, just ask!!!
From the FSM wrote:
Ignition Switch On (Engine Off)
When the ignition is turned on, the ECM activates the glow plug relay for a time period that is determined by engine coolant temperature, atmospheric temperature and battery voltage.
When the ignition (key) switch is placed in the ON position, a signal is sent from the sensors to the ECM relaying current engine coolant temperature and ambient air temperature (See Chart below:).
After receiving this signal, the ECM will determine if, when and for how long of a period the glow plugs should be activated. This is done before, during and after the engine is started. Whenever the glow plug module is activated, it will control the 7 volt high amperage circuit for the operation of the four glow plugs.

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