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Need Help


D_R
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First off I want to say hi to the board. Just picked up my first lexus, it's a 93 ls400. Having some issues with getting the running lights to work. I've replaced the fuse and bulbs. I've inspected the bulb housings, the wire harness at the trunk hinge, and the bulb failure box. The switch operates the headlights and turn signals just fine. All brake lights illuminate when the pedal is pressed. Does anyone have any ideas on what I could be overlooking because I'm fairly stumped right now.

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The only lights that do not operate are the parking lights that come on when the headlights are turned on ( side markers, tail lights). Last night I replaced the tail light harnesses and bulb failure box. Parts came from known working parts car. The parts look near new and they did not change a thing. Is there some ground or relay that I'm missing that only effects the parking lights? I've been reading that a faulty ECU could cause weird electrical issues, anyone know if the signal runs through it?

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If you are "Kaz" on the Club Lexus site, you say that the dash will not dim(an important piece of information) nor will the running lights come on. I am wondering if it might be the daylight sensor in the dash itself. Are you Kaz? http://www.clublexus.com/forums/ls400/754476-got-my-first-lexus-ever-need-some-help.html

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Yes that's me, if it is indeed the daylight sensor how would I go about checking it out. I have searched for this and have found nothing regarding the first Gen LS. And please forgive me but would the light sensor effect the headlight switch in the on position and not just auto? I'm used to dealing with older cars with simpler electrical systems.

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In your CL post you mention that the dash will not dim and that's what gets me to thinking about the sensor. But that is just a guess as I try to piece together your symptoms.

I believe the sensor is toward the front of the dash near the VIN plate. You could check it by putting the lights in 'auto' and then covering it and uncovering it to see if the system responds (or pull in/out of a dark garage). It normally takes a minute or so to respond so give it plenty of time.

I tried to find schematics for your car so I could see what is controlling the lights but I have not found any as of yet. I have the FSM for a 92(which should be the same) but the schematics are a joke and no lighting schematic. If you can find help with finding the schematics, this issue can be logically traced down.

[edit] Did a little searching and found a thread with some schematics. The side marker lights have a common ground behind the front right fender. Wonder if that is intermittent? Here is the link to schematics...there is also a link to a .pdf but you have to read closely -> http://www.clublexus.com/forums/ls400/396283-headlight-wiring-diagram.html

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The headlights do respond on auto, but that is still all that is responding. I'm going to check that side marker ground to see if that's the issue. Where exactly is the ground located, I have yet to find a decent repair manual for these cars so I've been kinda flying blind on these repairs

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I believe the ground is behind the plastic inner wheel cover so you will need to remove the wheel and plastic and have a look. Might be corroded. Let's hope that's what it is. Otherwise, could be some sort of control relay or module.

If you do remove the cover, try to snap a picture and post so that we can see what the connection looks like.

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OK got some time today, I'm not sure what I should be looking for my computer is down and it was impossible to read the wiring diagram on my phone. I took pictures of what I could see.

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I do not see a ground connection in those pics but everything else looks pretty clean. You might pull that connector apart and examine it and clean it while you have access. But otherwise, nothing stands out as being corroded. Back to square one, I guess...staring at the schematics.

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I've pulled every connection that I have come across just to check for any signs of a short or corrosion. So far everything looks good. If everything goes as planned tomorrow I should get the switch replaced. Hopefully that is the issue, either way I'll let you know.

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