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Hello again everyone, my 91 LS400 has a tail light issue the likes of which I've never heard of... When the headlights are on the tail light doesn't work on the driver side. And it's only a portion of the tail light as well, the lower portion, if it matters.
Hello again everyone, my 91 LS400 has a tail light issue the likes of which I've never heard of... When the headlights are on the tail light doesn't work on the driver side. And it's only a portion of the tail light as well, the lower portion, if it matters.
This sounds familiar to me.. If the light works when the headlights are off, but doesn't when the headlights are on, and/or it seems that only one of the two filaments is working in the bulb, it could be a grounding issue with the bulb socket for that tail light.
I faced an issue on another 91 LS, where the brake lights would all work with the headlights off, with one bulb being slightly dimmer than the rest, and then only the parking light would work with the headlights on at night. When the brake lights were on with the headlights, the same bulb would go out completely in that section. It all ended up being due to poor assembly of the ground wire in the bulb socket from the factory.
This sounds familiar to me.. If the light works when the headlights are off, but doesn't when the headlights are on, and/or it seems that only one of the two filaments is working in the bulb, it could be a grounding issue with the bulb socket for that tail light.
I faced an issue on another 91 LS, where the brake lights would all work with the headlights off, with one bulb being slightly dimmer than the rest, and then only the parking light would work with the headlights on at night. When the brake lights were on with the headlights, the same bulb would go out completely in that section. It all ended up being due to poor assembly of the ground wire in the bulb socket from the factory.
Note that you don't need to remove all of the carpeting and the rear trunk trim, as the guy does in the video. You can just pull back the carpeting on the side you want to work on, and access the two side bolts from there. Don't over-tighten them on re-installation, as the lenses are old plastic.
it is also common for 1st gen LS400s to have a brittle trunk wiring harness.
check the wiring harness at the hinge of the trunk as it goes into the car.
constant open/close causes the brittle wires inside the wiring loom to break and cause shorts.
might be worth looking into as well.
Another comment is that you *should* get a warning light on the dash when either a taillight or a brake light has failed. If you're not getting that warning light, it might be useful in debugging.
More specifically, that warning light (orange) is supposed to come on when the light is tried to be turned on but fails. So a failed brake light would come on when you step on the brakes for the first time after turning the car on. And a failed taillight would come on when turning the headlights/parking lights on.
I should have mentioned the warning light. The fix I mentioned might still work, but you should be seeing the tail light warning light on your dashboard, as I did. If the warning light is not on, it could be related to another issue.
Here is what it looks like on the LS 400 and on other Lexus/Toyota cars:
Also, timmy0tool's mention of the trunk wiring harness inspection is significant. Note that the outer lights are separate from the trunk harness, but it's always good to check that for any electrical shorts.
05-26-18, 10:30 PM
Tail light strange issue
