M318F, M320F and M322F Wheeled Excavators Hydraulic System Caterpillar

Electronic Control System

Illustration 1	g03702004
Diagram of the machine control electronic communication system (1) Machine ECM (2) Implement ECM (3) Travel Pedal (4) Engine ECM (5) CAN A data link (6) Machine Monitor (7) Machine security system (8) CAN B data link (9) Operator control panel (10) Product link (11) Service connector (12) Communication Adapter III (13) Electronic Technician (ET)

The following will cover information that pertains primarily with the pilot system and components that are controlled by the machine ECM and the attachment implement ECM.

When using this manual for the troubleshooting of the electrical system circuits, the complete electrical system schematic for your machine should also be used. Quick reference electrical connection diagrams are included throughout this manual. However, these diagrams do not show the machine wiring harness connections that are part of the circuit. The complete electrical system schematic illustrate all machine wiring harness connectors and the locations on the machine.

Electronic Control Module (ECM)

Illustration 2	g03701860
Electronic control modules are located to left rear side of the machine (1) Machine ECM (2) Implement ECM

Machine ECM

The machine ECM is the control module that will use the programmed control logic to manage the operation of most of the machine functions. The machine ECM will use the data from the various input devices to determine the appropriate output response to operator commands.

The machine ECM determines all of the appropriate output commands and communicates this information to the Implement ECM on the SAE J1939 (CAN) data link.

The machine ECM will activate outputs in order to energize or de-energize solenoids that will control the installed machine functions.

Except for the operation of the engine, the machine ECM will control the major machine functions on the machine. These functions include the following:

• Electronic shifting of the transmission and travel functions

• Left and the right electronic joystick operation

• Oscillating axle operation

• Implement control

In addition, the machine ECM will control the following attachment functions when installed on the machine:

• Quick coupler

• Medium pressure hydraulics.

• Auxiliary hydraulics 2 (2nd high-pressure hydraulics)

• Overload warning

• Travel lock

• Travel alarm

Illustration 3	g03701879
Machine ECM connectors (1) J1 connector (2) J2 connector

Pin Locations for Machine ECM

Illustration 4	g03701995
Machine ECM connector (70-pin)

Implement ECM

When the implement ECM is installed on the machine, the ECM will be used as a secondary control module to the primary machine ECM.

The implement ECM is used to control the outputs that are used for the attachments that are listed above. The implement ECM controls the outputs based on the command information that is received from the machine ECM. The implement ECM receives no input data from any external devices other than a key switch input.

The implement ECM will activate outputs in order to energize or de-energize solenoids that will control the installed machine functions.

The machine will be equipped with the implement ECM in order to control any of the following attachments when installed on the machine:

• Auxiliary hydraulics (MCV)

• Joystick steering

• Ride control

• Smart boom

Illustration 5	g03704942
Implement ECM

Pin Locations for Implement ECM

Illustration 6	g03704949
Implement ECM connector (70-pin)

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.

Sensor Inputs

Most sensor input circuits have an internal ECM "pull up voltage" that is present at the ECM contacts. An above normal voltage is internally connected to the ECM input circuit through a resistor. During normal operation, the sensor signal will hold the circuit at a certain signal amplitude. However, conditions such as a loss of power to a component, a disconnection, or an open circuit allow the circuit to be pulled high. The circuit is pulled high by the ECM pull up voltage. This situation will result in an above normal voltage condition at the ECM contact. As a result, the ECM will activate an FMI 03 (voltage above normal) diagnostic code for the affected circuit.

The types of ECM input sensor circuits that have pull up voltage present are:

• Pulse Width Modulated (PWM) sensor input circuits

• Active analog (voltage) input signal circuits

• Passive analog (resistance) input signal circuits

Pulse Width Modulated (PWM) Position Sensor Operation

When powered up, the position sensors continuously send a Pulse Width Modulated (PWM) square wave signal to the ECM. Any movement on a specific axis is detected by the position sensor for that axis. The duty cycle of the PWM sensor signal changes depending on the direction and amount of movement on the axis. The duty cycle is the percentage of time that the signal is high verses the amount of time the signal is low for one cycle. The more time that the duty cycle is high, the greater the percentage of the duty cycle will be.

The percentage of duty cycle signal for a typical position sensor will be recognized as valid is 10 ± 5 to 90 ± 5 percent. These percentages occur the extreme ends of the axis movement. A typical joystick thumbwheel that is in the center or neutral position would result in a duty cycle signal of approximately 50 ± 5 percent. For a foot pedal that is not depressed, a typical duty cycle signal would be 10 ± 5 percent. The duty cycle would be 90 ± 5 percent when the pedal is depressed.

The position sensors are calibrated by the ECM to relate a specific duty cycle signal to a specific axis position for the device being monitored.

The ECM will convert the duty cycle from the position sensor to a calibrated duty cycle signal. The ECM uses this signal and a software "map" to determine the appropriate output signal that will be applied to an output device.

Note: None of the PWM sensors on the M300F Series machines require manual calibration. The machine ECM will perform an automatic calibration procedure at ECM power up.

The pilot system contains the following sensors:

• Travel pedal position sensor

• Auxiliary hydraulic pedal position sensor

Pressure Switches

Illustration 7	g02332474
Pressure switch

Note: The values in Table 4 are for bench testing only. Values may not represent parameters for machine systems specifications.

The pilot system contains the following pressure switches:

• Boom down pilot pressure switch (smart boom application only)

• Swing pilot pressure switch

Outputs

The ECM responds to inputs by sending electrical signals to the outputs. The outputs can create an action or the outputs can provide information to the operator or service technician.

On/Off Solenoids

For control of on/off type solenoids and relays, the ECM will either turn ON or turn OFF the output for a component. The output command is based on the signals from the input devices that are involved in the system. The ECM will not vary the amplitude of the output, the circuit is either energized (on) or the circuit is de-energized (off). When the on/off output circuit is energized, most often system power will be used to energize the circuit and the output component.

Illustration 8	g01158530

Note: The values in Table 5 are for bench testing only. Values may not represent parameters for machine systems specifications.

The pilot system contains the following on/off solenoids:

Pilot manifold integrated

• Heavy lift

• Implement lockout

• Medium pressure/pilot pump displacement control

• Oscillating axle

• Swing brake

• Travel direction

• Transmission gear shift 1 and gear shift 2

Free positioned in machine

• Smart boom

• Joystick steering (1st gear restriction)

• Quick coupler

• Blade/stabilizer activation (undercarriage)

Service brake valve integrated

• Auto brake

Multi combined valve integrated

• Uni/bi-directional oil flow

Proportional Solenoid Valve

Illustration 9	g02703776

Note: The values in Table 6 are for bench testing only. Values may not represent parameters for machine systems specifications.

The pilot system contains the following proportional solenoids:

Pilot manifold integrated

• Main pump displacement control

• Swing pump power shift control

• Travel pilot pressure modulation

• Travel motor displacement control

Free positioned in machine

• 2nd high pressure circuit A (attached to main control valve)

• 2nd high pressure circuit B (attached to main control valve)

• Fan pump displacement control

• Joystick steering A (medium pressure valve block)

• Joystick steering B (medium pressure valve block)

• Medium pressure A (medium pressure valve block)

• Medium pressure B (medium pressure valve block)

• Multi combined valve A (auxiliary flow valve A)

• Multi combined valve B (auxiliary flow valve B)

• Multi combined valve A (line relief pressure A)

• Multi combined valve A/B (working pressure cut-off)

• Offset boom A (medium pressure valve block)

• Offset boom B (medium pressure valve block)

Soft Switch Panel

Illustration 10	g03708249
Soft Switch Panel (1) Oscillating axle control button (2) Travel speed control button (3) Creeper speed control button (4) Ride control button (5) Parking brake control button (6) Smart boom control button (7) Overload warning enable control button (8) Swing lock control button

Pin Locations for Soft Panel Switch