Multiple tail light failure relay box failures.
 

1992 LS400. About 150,000 miles. Have replaced the small tail light failure relay box in trunk (89373-50010) multiple times. The unit installed when new in 1992 lasted 20 years. My second box lasted about 9 months. My third box about 2 months. My fourth box lasted exactly 1 day. My fifth box lasted exactly 2 days.

Am I suffering from the notorious fraying of one or more wires in the trunk hinge wiring harness/bundle? If so, is it possible to simply replace the whole wiring bundle with a new part from Lexus? If so, what is the correct part number?

Many thanks in advance to the many experts here. I'd really like to replace the whole wiring harness in one fell swoop, rather than have to go spark chasing with individual wires for the rest of my life.

If the wiring harness is discontinued/out of production, could I construct a wiring harness to replace? I can't possibly be the only person wanting a more permanent fix for that troublesome trunk hinge wiring harness. Has anyone else tried to make their own replacement wiring harness?

My recollection of the threads is that members have gone in and fixed those particular sections of the harness where the wire/s sheath has worn causing the shorting. Curious to see pics of that area if you could take some.

Thanks RA40. I'll go in and see if it's actually just insulation worn away.

Well, I went in and unclipped the bundle from the harness and had a look. This is not a simple procedure, at least for a non-mechanic like me. I've searched the threads and haven't found any pictures or video clips showing how to do this. I wish there was.

Since my only problem is apparently shorting out the relay box for the tail lamps, I might just leave it be. I'm afraid if I start to go down the route of taking apart the harness and undoing the tape, etc..., that I might do more damage and actually break some wires that are now intact. I'm not presently having the driveability issues that other threads have described. If I were to develop those more serious issues, I might actually try to attempt this fix. But I think I can live with the car as is.

Anyone have any thoughts?

bumping up ...