My VSC and ABS lights sometimes come on at the same time, and then they
> go off again together. Then they come back on again later.
> I took it to the local Lexus dealership and they hooked up a handheld
> computer to get the code, but no code was indicated. They are puzzled
> and suggested that I bring the car in for further diagnosis.
> Any clue on what may be happening?
>
> Sometimes I could feel the ABS system activating when I press on the
> brakes. Right after that, the lights would come on together. But
> sometimes the lights would come on even without the ABS system being
> activated (as far as I can tell of course).
>
> This is a 1998 Lexus LS400.
>
> Thanks
>
I believe that the trouble codes for those problems have 2 trip detection logic, where the computer has to see the same problem for 2 consecutive trips to turn on the lights and conversely, if the problem is absent for 2 consecutive trips, the light will turn off.
In order to read a trouble code, it has to be stored in the computer's memory, and a sign that a trouble code is stored din the memory is having the lights on. In other words, you have to read the codes while the lights are on.
I suspect that a component that is common to both the ABS and VSC, like a wheel speed sensor, is beginning to fail. If that is the case, the lights will come on more consistently.