950M and 962M Wheel Loaders Power Train, Steering, Braking, Hydraulic, and Machine Systems Caterpillar

ECM

Illustration 1	g03389636
(1) Connector view from ECM side (2) Connector view from harness side

The ECM decides based on input information and memory information. After the ECM receives the input information, the ECM sends a corresponding response to the outputs. The inputs and outputs of the ECM are connected to the machine harness by two 70 contact connectors (J1 and J2). The inputs and outputs to the ECM can be viewed through the Caterpillar Electronic Technician (Cat ET).

Note: Only the complete ECM is serviced (no lower levels components). The ECM must be replaced if the ECM is damaged. Replace the ECM if a failure is diagnosed.

Pin Locations

Inputs

The inputs describe the status of the machine systems. Two types of inputs exist. The inputs can be either a switch type or a sensor type. Switches provide an open, a ground, or a + battery signal to the inputs of the controller. Sensors (frequency, PWM, or voltage) provide a changing signal to the sensor inputs of the controller. The inputs to ECMs are listed in table.

Temperature Sensors

Axle Oil Temperature Sensor

Illustration 2	g03389644

The temperature sensor for the hydraulic oil informs the ECM of the temperature of the hydraulic system oil.

The sensor sends a PMW signal to the Transmission ECM indicating axle oil temperature. The duty cycle range for this sensor is 10.01% at −40° C (−40° F) to 89.26% at 120° C (248° F).

The Brake System uses one temperature sensor for the front axle oil and one temperature sensor for the rear axle oil.

Pressure Sensors

Illustration 3	g03389651

Brake 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.

Position Sensors

Illustration 4	g03389655

Torque Converter Pedal Position Sensor

The pedal position sensor determines the position of the torque converter pedal. The sensor sends a PWM signal to the power train ECM. The power train ECM monitors the signal. Then, the power train ECM calculates the position of the pedal from the signal.

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.

Service Brake Position Switch

Illustration 5	g03389656

The 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	g03389659

The 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	g03389665

The 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	g03389670

The 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 link uses the connector for the service port in order to communicate with the Caterpillar Electronic Technician. A data link connection is provided for the product link.

Note: The control for the product link provides a global positioning system for the machine.

The data link is bidirectional. The bidirectional link allows the ECM to input information and output information. The data link consists of the following parts: internal ECM circuits, the related harness wiring, the service tool connector and the connector for the product link.

• The ECM receives commands from the Cat ET in order to change the operating modes. The Cat ET will read the service codes that are stored in the memory of the ECM. The Cat ET will clear the service codes that are stored in the memory of the ECM.

• The ECM sends the input and the output information to the Caterpillar ET.

Note: An electronic control module that uses the Cat Data Link will have a module identifier. The MID for the Transmission Electronic Control Module is 051. The MID for the Implement Electronic Control Module is 052.

CAN Data Link

A data link is required for communication with the service tool (Cat ET) and the electronic control modules. The data link also communicates with the instrument clusters and other devices using this communications protocol. The data link is not used in order to broadcast any diagnostic information.