New car customers complained bitterly that they couldn't turn it off. This is how we did it before the factory came up with their plan that costs a fortune.
Install any kind of switch you like, anywhere you like
Give it power from any convenient source, run the other end down to the TCS ECU
Find the Brake Light signal wire that goes into the TCS ECU
Splice in the switched power wire you just made
Install a diode (Radio Shack Generic) between your splice and the rest of the Brake Light circuit so that your switch cannot illuminate the Brake Lights.
When you turn on your new switch, you will be sending a Brake Light signal to the TCS ECU but not the rest of the car.
TCS will think you are braking and turn itself off, the rest of the car won't know you're lying to TCS.
Not quite.
TCS and ABS share the wheel speed sensors.
ABS makes sure one wheel doesn't go slower than the others.
TCS makes sure one wheel doesn't go faster than the others.
The car assumes you want TCS unless you ask for ABS.
You ask with the brake light circuit.
So,
In normal operation you have TCS until you step on the brake, at which point all systems prepare to brake, TCS sees this and turns itself off.
With your new switch, TCS will always think you're preparing to brake.