Brake switch monitors malfunction of Accelerator Pedal position Sensor (APS). APS and brake switch is consist of two circuits (APS 1, 2 or Brake switch 1, 2) that operate independently of each other to confirm output signal. Drivers depress brake pedal when 1) the voltage higher than driver's intension is detected due to APS malfunction (signal circuit short to high voltage) 2) engine power generates excessively due to fault signal. Like previous example, if driver's intension to decelerate is transmitted to ECM (brake pedal depressed) when APS signal is high, ECM consider APS to be fault and Limp Home mode is activated. When Limp Home mode is activated, engine speed is fixed at 1200RPM and driving performance is limited, later, if correct APS signal is detected, Limp Home mode is deactivated immediately.