BOLT 4M9742 - Caterpillar

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Key Start switchWhen the "Key Start" switch is moved to the ON position, a system voltage input 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 occurs, each ECM will initialize and then become operational.When the Key Start 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 to the ECM to transition from the operational mode to the sleep mode. The ECM will perform some internal power down procedures and then enter the sleep mode.The transition period from the sleep mode to the operational mode happens in a very short period of time. When the Key Start Switch is moved to the "START" position, a system voltage input will be provided to the machine ECM start contact. When the ECM detects the voltage in the circuit and the machine systems start status is correct, the ECM will initiate the engine cranking sequence. The key start switch circuits are not monitored for diagnostics by the machine ECM.Parking Brake Switch Inputs
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Parking brake switch input connections to the machine ECM
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The parking brake switch is located under the cover for the "Operator Left Control" handleThe 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 hydraulic oil in the brake system is directed to the hydraulic tank which will result in the parking brake being engaged.Under certain machine conditions, the machine ECM can override the parking brake Switch and energize the parking brake solenoid with an ON/OFF type output that is connected to the solenoid energize circuit.Blade Control Handle Switches
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The machine ECM will respond to the duty cycle of the pulse width modulated (PWM) signal by sending a specific level of electrical current to the appropriate proportional solenoid valve. The decision is based on the information that is contained in the software of the ECM. Autoshift Switch
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The autoshift switch or the Advisor informs the ECM that the operator wants the autoshift function to operate. The following selections can be made when the switch is activated sequentially:
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Location of "Autoshift" switchThe autoshift function can be turned ON and OFF with either the advisor or the switch (see above). The switch only toggles between ON