Hi all, haven't posted in a while about my 98 LS400. I recently started having an issue with the auto headlights not shutting off after leaving the car.
I know the first thought would be door, trunk, hood sensors. Tested all of them and they work normally. Open door/trunk/hood indications in the cluster also work normally.
Here's the most interesting part -- even with a door ajar, you can normally kill the lights by arming twice. This no longer works... the lights stay on no martter how many times you arm.
They turn on/off normally while driving depending on light level -- they only stay on and refuse to extinguish when shutting down after dark, and will run the battery completely flat unless manually shut off.
Thanks for any clues!

 

I used to have this issue from time to time. I would just manually shut them off. Sometimes they would go off and other times they would not. I never did anything to fix it and just chalked it up to the car being old.

 

Sounds like a problem in the headlight delayed turn off circuit; I'm not sure if it uses a physical relay, or a solid-state control, but it's stuck on, which bypasses all the other controls, except the OFF switch.

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Anyone know which module controls this? I wonder if I have degraded caps, ect.

 

Body ECU?. Some factory wiring diagrams to assist in your trouble shooting efforts...

 

Thank you YODAONE!
So looking at the diagrams it seems the culprit is most likely the "body ecu"?

 

The Light Control Switch connects to body ECU.

 

At first I'd check the relay's contacts to see how one side is convex (pip) and the other concave (crater). I have seen many relay problems such as a situation of dog's intercourse.
This is common problems among aged DC relay's contacts that carry big current.

 

"situation of a dog's intercourse" . Never ran across that one before, although I've often filed relay contacts to remove deposition fouling deposits. Wish I could find an emoji for that!

 

http://www.esterline.com/Portals/3/H...ure%203.1c.jpg