Hey guys,
First off, this might get a little long on the posting side. I will try to keep this some what ordered. The problem appeared yesterday evening when I was on my way to the gym. I previously that evening drove home from work in terrible tropical storm/hurricane like rain. A bit of background is I also removed the cover which goes underneath the engine bay as it was starting to sag a little bit.

Initially I thought the problems I am encountering were a result of a or a few computers being flooded from the rain and wind.

I will start with the exterior problems: The problem I noticed on the exterior would be my break lights. When I have my headlights/parking lights on, and press the brakes, all light up, except the ones which are attached to the trunk. They just go out.

As for the interior problems, there are a few. First off, when I press the brakes, the "R" light for reverse lights up on my console. Also the dead brake ligt comes on. Now along with this, if I have my headlights/parking lights on, when I press the brakes, my cluster dims out to almost off, and all the green backlights on the stereo go off. I do notice that when I shift gears, I hear a little rattle noise, most likely from the shift lock release assembly.

Now on to mechanical. When I apply breaks while driving, the car automatically downshifts if in a gear higher than 1. This causes the car to jerk as it is slowing down. Naturally the RPM's jump up when it downshifts to a lower gear.

I have no idea how to tackle this problem. I do not know if it is a transmission problem, ABS problem, electrical short, or something else. Natually I did not know the right place to post, so I posted it here. Hopefully someone can help diagnose the problem, or point me in the right direction. Any help would be much appreciated. The car has almost 160K on the clock, and I would like to see it go much higher before I have to sell it.

Thanks again.
-R

 

you have a broken wire in your back left trunk hinge

 

It just so happens that I have encountered the same problem last year, so I took it to my local Lexus dealer and gave me some B.S. that it was my break light unit that is located in the trunk lid was shorted out. So I figured in the past when I would replace the bulbs that I noticed that this unit is held with just 2 screws. I advised my Lexus sevice manger that I will buy the unit that is required and I will replace it myself. When I got home that day it was a very simple "plug and play".......... but the problem did not go away. I brought it back and they could not figure it out?!?!?!? We pay these mechanics so many $$$ per hour and they could not figure it out??? I was pissed and made a little scene b/c I waited a while for them to diagnose the whole deal, and still no go. They told me to leave it with them for the day as I had to go to work. I grabbed my gym bag in the trunk, but as I grabbed my bag I noticed something with the wires that is located in the left arm of the trunk lid. For starters it's the wires that leads to the break lights of the trunk lid covered in a black strip of plastic, so I yanked it out in front of the service manager and other customers, too soon discover right there and then that over time one of the wires from natural wear and tear of bending by opening the trunk, caused a break right across one of the wires where @ times it would make proper contact, but then @ times would make contact to the "METAL ARM OF TRUNK!!!" creating a electrical grounding effect which in turn caused a daisy chain of events. Which just so happens to be the same deal you are experiencing. But the "R" that appears should be a big concern, Why? Put it this way if you a driving especially fast on the highway that last thing you would like to do is drop the gear into "Reverse!!!" B/c cause of this one slice of the wire when you brake you are sending positive power to the break lights but in this case it is getting grounded! Creating feedback causing the computer to be fooled, allowing to bypass and making the tranny to try or will drop into reverse and that is what causes the jerk. In the end they fixed the cut wire and guess what every problem was gone! And I got a refund on that unit they told me was short! The simple fact I was able to still use the old one based on the problem being a cut wire. All I can say is do not drive for now till you fix the problem and I hope it is the same deal that I had so it can be fixed right away, and to all 1st generation LS400 owners look out for this, as I am not sure with the later generations would be applicable as I am not aware of how the wires is run through the trunk to the break lights, probably the same way. And I apologize to all ClubLexus members who have to read this "extensive reply/advice" as I thought to share this one with everybody. And avoid such costly tragedy, of something so small and unthought of can lead to be the biggest problems!

 

Darkside,

I recall seeing this in other posts last year, and you are right on the money. One of the Lexus techs on the forum gave this same advice to a member ( I noticed Sooner was all over this like Roseanne Barr on a twinkie )and it fixed all kinds of problems on his first generation LS400

rajah996,

I strongly recommend disconnecting the negative battery terminal before tackling this (and any electrical work). Not only does it make it safer, it gives all your ecu's a chance to reset after this problem, where they may have lost ground and had some abnormal voltages coming in to them.

 

Hey guys,
Thank you all for your quick and informative replies. What I did was
first replaced all the brake light bulbs. I noticed during this problem
that some were really bright (more than normal), some lit up normal
and some were really dim. I just changed them all. I also then checked
the wires, and found a small splice. A little electrical tape, and am good
to go. Took her for a spin and did not experience any of the problems. I
will test her out once again tonight, so I can see if the stereo lights are
acting up, or if that has been fixed too. Again thank you all for your help.

-R

 

Awesome info, Ill be checking that out in a bit. BUt please!!! PARAGRAPHS!