COVER AS 1568851 - Caterpillar

Illustration 3 g03389651Brake Pressure Sensor
The brake pressure sensor informs the power train ECM of brake system pressure. The pressure sensor output is a pulse width modulated signal. The duty cycle of the signals will vary in proportion to the system pressure. These PWM signals are inputs to the Power train ECM. The Power train ECM provides 8 V supply and 8 V return for the sensor.Switches
Switches provide one of the following types of input to the ECMs.
Open
Ground (-)
Battery (+)Switches are devises that have two states, Open and Closed.
When a switch is open, no signal is provided to the corresponding input of the ECM. This condition is also referred to as floating.
When a switch is closed, a ground signal (-) or a battery signal (+) is provided to the corresponding input of the ECM.Parking Brake Switch
Illustration 4 g03431151The parking brake switch is a two pole switch. The switch has a common return for both poles of the switch, and three ECM contacts. Two of the contacts are on one pole and are a normally open and a normally closed contact. In the normally operating position, the normally open contact floats to a high voltage state and the normally closed contact is pulled to a low voltage state. The last ECM contact is an additional normally closed contact. When the switch is activated the normally closed contacts float to a high voltage state, and the normally open contact is pulled to a low voltage state. By monitoring the voltage state of the three ECM contacts, the ECM is able to determine the operator request for parking brake.Service Brake Position Switch
Illustration 5 g03389656The brake pedal position switch is a mechanical switch that is used to determine if the operator is depressing the service brakes pedal. This switch has two outputs, one that is normally closed and one that is normally open. This switch provides a ground signal to the engine ECM. When the operator activates the switch, the outputs become reversed.Parking Brake Pressure Switch
Illustration 6 g03389659The parking brake pressure switch is a pressure switch that is used to indicate to the power train ECM if the parking brake pressure is present. This switch has two outputs, one that is normally closed and one that is normally open. This switch provides a ground signal to the power train ECM. When there is pressure applied to the switch, the outputs become reversed. Brake Accumulator Pressure Switch
Illustration 7 g03389665The brake accumulator pressure switch is a three wire switch. There is a normally closed contact, normally open contact, and a common contact. The brake accumulator pressure switch sends a ground (-) signal to the power train ECM when the brake accumulator pressure is below a preset value. The normally closed contacts are not used in this application.Ignition Switch
Illustration 8 g03389670The ignition switch is a four position, two contact switch. The transmission ECM receives battery (+) voltage from the ignition switch in the (RUN), (START), and (AID) positions.Data Link
Cat Data Link
The Cat Data Link is an input/output of the ECM. The data