I have a 2010 Lexus LS460-L. It is a nightmare. I can drive it 100 miles or sometimes 800 miles, and then when I am stepping on the brake, all the brake lights come on and the brakes catch and release like a wave motion at speeds under 15 mph until the computer gets reset by the service department, and it is good for another 4-6 weeks, when it reoccurs. I have had it in to Toyota 5 times. Computer diagnostics fails to find the problem. I have paid to replace the master brake control module (ECU) and the stroke sensor. I had it in to the Lexus dealer in Kansas City, and they said that their diagnostics failed to find the problem, and the "only thing they could think of" is to replace the wiring harness, for $13,000, and of course they don't recommend spending that much money on it. I was skeptical, so I took it to the same dealer's other location, and the service man there told me that their diagnostic tests are "pointing to the wiring harness". Is it even possible for the computer diagnostics to point "to the wiring harness"?

 

The braking is a brake by wire system backed up by a hydraulic mechanical system.
I believe the diagnostics cannot point to a bad harness (I could be wrong) but the tech can draw an inference from the data or they have experience with the issue. It could also be that they don't really know since everything checks out and the weakest point that can be prone for intermittent issues is the wiring harness.

I cant believe the wiring harness is $13,000. If it were me and I suspected the wiring harness I would take an ohm meter and check the resistance of each contact until I found the weak contact, repair and move on.
Or I would check salvage for a harness for a few hundred dollars.

 

If its the harness, then they can trace and pinpoint the problem for a lot less money and time than replacing it. Do you know what's involved replacing a car's wiring harness? That's why its $13,000!

Go to a reputable independent; they can usually solve problems the dealer has given up on.

 

Has anyone checked the connectors for the brake system? Unplugged and reseated each to eliminate a corrosion problem?