If two of 4 sensors are EGR and Quick Warm Up, then most of us would be able to remove or re-use 2 these threads for other applications.
From previos posts and my own experience with the glow plug system this is what i've got:
1) ?
2) Glow plug sensor
3) ?
4) Temp gauge sensor
Can anyone fill in the blanks? I've looked all through my 4JB1T manual and can't find anything more.