GASKET 1192948 - Caterpillar

ECM Pull Down Voltage
To aid in diagnostics of electrical circuits that are controlled by the ECM, an internal "pull down voltage" is connected to ECM switch to battery type input circuits. During normal operation, the switch contacts that are allowing the connection to a voltage source will hold the circuit high. When circuit conditions such as a loss of power to the switch supply voltage, a disconnection in the switch circuit or an open circuit will allow the circuit to be pulled low by the ECM pull down voltage. The pull down voltage will result in a below normal voltage condition at the ECM contact. As a result, the ECM will activate an FMI 04 (voltage below normal) diagnostic code for the affected circuit. Inputs
The machine has several different types of input devices. The ECM receives machine status information from the input devices and determines the correct output action needed to control machine operations. The output is based on memory and software parameters. The machine utilizes the following types of inputs: switch type and sensor type. Switches provide signals to the switch inputs of the ECM. The possible outputs of a switch are listed: an open signal, a grounded signal and + battery signal. Sensors provide an electrical signal to the ECM that constantly changes. The sensor input to the ECM can be one of several different types of electrical signals such as: pulse width modulated (PWM) signals, voltage signals and frequency input signals. Each possible input to the Transmission/Chassis ECM is listed in the tables for the 70-pin connectors.Outputs
The ECM sends electrical signals through the outputs. The outputs can create an action or the outputs can provide information to the ECM. The ECM can send output signals to the system components in one of several different electrical signal types such as: driver outputs, sinking driver outputs, sensor power supply outputs and data link outputs. The possible outputs for the Transmission/Chassis ECM are listed in the tables for the 70-pin connectors.Input/Output
Communication between the Machine ECM and the other control modules on the machine is conducted over data link circuits. The data link circuits allow the sharing of information with other electronic control modules. The data link circuits are bidirectional. The data link circuit allows the ECM to send information and to receive information.The ECM supports two types of data link systems.
Cat Data Link
SAE J1939 Data Link The two types of data links are the main structure for communication between all of the control modules on the machine. More than one CAN data link system can be present on a machine. Dedicated CAN data link circuits can be used for communication between specific controls on the machine.Communication between the Transmission/Chassis ECM and the other control modules on the machine are conducted over the J1939 Data Link circuit. The data link is connected to each control module. The ECM modules use the Cat ® Data Link to send and receive information from the Cat Electronic Technician (ET) Service Tool.A module