The Service Brake System Light Silverado comes on when you press on at least one of your car brake pads. To reset it, follow these steps, Turn the ignition key from OFF to ON 8 times within 10 seconds to activate ECM/PCM from sleep mode. Leave the key ON as you press and hold the brake pedal for a brief moment. Write the factory Mode S code from the instrument panel odometer with space and asterisk. Turn OFF the ignition key and then turn it ON after some minutes.