Have a 1993 Lexus Ls400 which has an unusual problem. While driving the other day, the Reverse light came on in the dash along with the Drive light. Car would only do 35 mph, can rev motor up to 6000 rpm and still no power. Transmission wants to change in and out of gears. Checked fluid, fine. Disconnected battery for 1 hr and car drives fine. Then two days later, same thing. Disconnected battery again and it runs fine again. Called dealer and they have never heard of the problem. Could it be a sensor, computer, switch, . . . . . .???

 

Vinnie,

Welcome to the forum. I remember hearing about this from a few other posts in the past. As crazy as it sounds, it is likely to be wiring in the left trunk hinge. As the bundled wires have been pulled and flexed over the years, a ground wire in there breaks. A search on this turned up these symptom descriptions from VVT-i, a Lexus Master Tech on the forum ......

"the ground wire that run inside the trunk lid also share the same ground with your Throttle Position Sensor and some other sensor as well. It will not show on the wiring diagram, but some times you step on the brake, your Reverse light on the combination is comes on or some of the tail light is dimmer than other. Some funky stuff..
Open the trunk, under the left side of the hinge, you'll see the harness and a small plastic cap ( U shape). Open that U cap you may find some of the wire(or wires) is broken from the trunk being opened and closed for so many hundred times and it will stress the wire after the period of time.
I hope this may help. Please let us know what's going on.
Good luck"

A very informative thread is here https://www.clublexus.com/forums/sho...unk+hinge+wire

Let us know how it works out.

Regards,

GA400

 

GA400, Opened the trunk lid and sure enough there was a broken white wire in full view. Repaired it and so far so good!! I sure do appreciate it!!.

 

Holy toledo what an obscure fix that was!

Vinnie coulda wasted hundreds of dollars on clueless mechanics trying to figure that one out, but thanks to GA400, it was fixed for FREE!

 

Who would have thought!
Is this problem isolated to the first gen or has it occured with any later ones? This is a good one to file away.

 

Well, all the problems I've seen are from the 1st gen LS only. Sometimes you will see about 4-5 wires broken and when you step on the brake the Reverse light comes on. For some reason the broken wires in the trunk has some feedback directly to the TPS( to down shift of some wierd stuff in the trans.) and the dash lights.