1993 f-super duty (f450) idi diesel w/e40d.
1.i have a good 20a amp maxi fuse.
2.i have a good ecc relay.
3.i have tested the OD switch/light in my other truck ('93 f250 idi diesel e40d) and it works ok.the good one from the other truck also glows dim if i put it in this truck.
4.the light is very dim.much dimmer than when you pull the fuse or relay to the trans.it's more of a glow with a slight flicker.to see it during the day,i have to cup my hands around it.
5.the trans works fine.all shifting seems normal.the od cancel button locks out od as it should.
6.i have full battery power and good grounds at the correct trans harness pins.
7.i have temporarily jumped power directly to the power line going into the trans harness with same results.
8.i have completely inspected the wire harness visually and all looks good.cleaned and applied dialectic grease to all plugs.
9.pulling the steering column apart and unplugging the od light switch plug,i have power at the white with green stripe (12V+) and power at the red with yellow stripe (14V+) but i also have power at the tan with white stripe pin.approx a 10th of a volt.all reading are with engine running.
im guessing this slight power source (10th of a volt @ tan/white) here is the reason for the slightly glowing OD light.
10.i checked all the ground pins with an ohm meter and they all seem to be fully grounded with nothing really showing up at least on a low end multimeter.
11.i have cleaned the grounds at the drivers side kick panel,and up by the drivers side headlight/radiator support/where it's also the grounding stud for drivers side battery.
i also cleaned the ground up by the upper drivers side hood hinge.

does all this lead to a bad trans control unit? or did i miss anything?

 

confirmed the ecm was going bad.i swapped them between trucks and the issue followed with the bad ecm,and disappeared with the good one installed.
reman ecm on it's way.