PUMP GP-AIR 4699378 - Caterpillar

When the "starter key" switch is moved to the ON position, a system voltage is provided to all of the control modules on the machine. The presence of this voltage input will cause each ECM to transition from the "sleep mode" (inactive) to the operational mode. When this transition occurs, each ECM will initialize and then become operational.When the "starter key" switch is moved to the OFF position, the system voltage is no longer present at the ECM "Key Switch - ON" input. The absence of the system voltage signals the ECM to transition from the operational mode to the sleep mode. The ECM will perform some internal power down procedures before entering the sleep mode.The period from the sleep mode to the operational mode happens in a short time. When the "starter key" switch is moved to the "START" position, an input voltage will be provided to the start contact of the Machine ECM. When the ECM detects that the voltage in the circuit and the machine status for the system are correct, the ECM will initiate the engine cranking sequence. The key start switch circuits are not monitored for diagnostics by the Machine ECM.Recall Switch
The Recall (Resume) Switch provides two switch-to-ground inputs to the Machine ECM. When the switch in not depressed, the normally closed switch input is grounded to the ECM return circuit. When the switch is depressed, the normally open switch input is grounded to the ECM return circuit. When machine travel has been interrupted and the switch is momentarily depressed, the ECM will send the last selected travel speed command to the Motor ECM in order to resume machine travel.The switch is also used as a set switch for setting the machine travel speed that is selected on the Travel Speed Thumbwheel. When traveling in the FORWARD or the REVERSE direction and the switch is pressed for 3 seconds, the Machine ECM will "set" the current speed as the selected speed for the current direction.The machine ECM expects only one of the switch input circuits to be grounded at a time. If both of the switch input circuits are grounded at the same time or if neither of the switch inputs is grounded, the ECM will activate a diagnostic code for the switch.Parking brake Switch Inputs
Illustration 10 g02576399
Parking brake switch input connections to the Machine ECMThe parking brake switch is a two pole switch. One pole is used to provide two, switch to ground inputs to the Machine ECM. The other pole is used to energize the parking brake Solenoid.The ECM monitors the position of the switch in order to determine the status of the switch and to detect a change in the switch state. During machine operation, if the operator presses the parking brake Switch in order to engage the parking brake, system power from the parking brake solenoid fuse is passed through the switch contacts of the energize circuit to the Parking Brake solenoid. When the Parking Brake Solenoid is energized, the