VALVE GP 9T0624 - Caterpillar

Brake Backup Pole
The brake backup pole of the parking brake switch operates independently of the ECM. The pole is a backup to the ECM and the ON/OFF pole of the parking brake switch. Normally, the ECM applies the left and right brakes according to the status of the ON/OFF pole. The brake backup pole ensures that the brake is engaged if either the ON/OFF pole or the ECM are not functioning properly. When the parking brake switch is in the ON position, the brake backup pole sends a +battery signal to the parking brake solenoid. The parking brake solenoid engages the left and right brakes. The fuse for the ECM is the source of the +battery signal. Note: The parking brake solenoid is also connected to the ECM. The ECM will send +battery voltage to the parking brake solenoid if the signal for the brake backup pole is not at +battery voltage and the parking brake switch is ON. Note: The ON/OFF pole diagnoses an INCORRECT condition of the brake backup pole. The ECM periodically checks the status of the ON/OFF pole and the output for the parking brake solenoid. The ON/OFF pole tells the ECM whether the parking brake switch is ON or OFF. If the ECM does not detect +battery voltage at the output for the parking brake solenoid and the parking brake switch is in the ON position, a diagnostic code for the brake backup pole is logged. See System Operation, "Diagnostic Operation".Note: On the 572R Pipelayer, the backup pole of the parking brake switch does not connect directly to the parking brake solenoid. The backup pole of the parking brake switch connects to an input to the ECM. The ECM controls the parking brake solenoid.Neutral Start Pole
The neutral start pole of the parking brake switch operates independently of the ECM. The neutral start pole ensures that the parking brake switch is ON before the engine will crank. When the parking brake switch is in the ON position, the ECM shifts the transmission to NEUTRAL and the ECM activates the brakes. When the parking brake switch is in the OFF position, the neutral start pole opens the start circuit between the key start switch and the start relay. This prevents turning the starting motor. When the parking brake switch is in the ON position, the neutral start pole closes the start circuit from the key start switch to the start relay. This completes the circuit and the starting motor can turn. Service Brake Pedal Switch
Illustration 4 g00592713
Service Brake Pedal Switch
The service brake pedal switch operates independently of the ECM. The switch is a backup to the ECM and the brake pedal position sensor. Normally, the ECM applies the left and right brakes according to the position of the brake pedal position sensor. The switch ensures that the brakes are engaged if either the brake pedal position sensor or the ECM are not functioning properly. When the operator pushes the service brake pedal to near full travel,