This info might help out:
The Brake Override System operates when these
conditions are met:
1. The throttle opening is greater than 1/3
2. Vehicle speed is above 5 mph
3. Brakes are applied firmly
In order to activate the Brake
Override System, the accelerator pedal
must be pressed before the brake pedal.
Additional Details:
• During greater accelerator pedal application,
the Brake Override System activates with any
brake pedal pressure.
• Brake Override System activation is cancelled
when the brake pedal is released.
• When the Brake Override System is active at
part throttle, changes in the accelerator pedal
position may cancel activation.
• To allow the vehicle to start on a hill without
rolling backwards, the Brake Override System
will not activate if the brake is applied prior to
pressing the accelerator pedal.
• The Brake Override System is not active in
4WD vehicles while driving in low range.
• Note to Hybrid owners: The Lexus Hybrid
System achieves a result similar to the Brake
Override System by reducing power if the
brakes are applied while the accelerator pedal
is depressed.