980K Wheel Loader Electrohydraulic System Caterpillar

Illustration 1	g02461916
Components that are monitored by the Implement ECM to control the operation of the Payload Control System (PCS)

The Payload Control System (PCS) is an electronic system that will provide an accurate weight of the material that is loaded by a wheel loader. The PCS is controlled by the Implement ECM.

This section covers the operation of the input components that are used when the Implement ECM is controlling the operation of the Payload Control System (PCS). For instruction on the operation of the PCS, refer to Operation and Maintenance Manual, SEBU8551, "Payload Control System (PCS) (If Equipped)" and Systems Operation, Troubleshooting, Testing and Adjusting, UENR0359, "K-Series Monitoring System".

For the diagnostic code procedures and the event code procedures for components that are used in the PCS, refer to the Troubleshooting, KENR6483 manual. The manual covers all of the diagnostics and events that can be activated for Implement ECM controlled components.

PCS Input Components

Operator Interface
Controls

Illustration 2	g02461936
Keypad 8 PCS buttons (1) PCS reweigh button (2) PCS clear / zero button

The electronic Keypad 8 enable the operator to indicate the PCS commands to the Implement ECM.

The keypad communicates the PCS operator commands to the Monitoring System Display and the Machine ECM on the CAN A Data Link communication system. The Machine ECM will then distribute the PCS button status to the Implement ECM on the data link system. The Implement ECM will then act on the PCS command accordingly.

The Implement ECM does not monitor the Keypad 8 buttons for diagnostics.

Illustration 3	g02461937
Right-hand console with the standard lever controls and the attachment implement control joystick (3) Location of the PCS Store Switch

Illustration 4	g02461958
PCS Store Switch connections

The PCS Store Switch is installed on the machine when the payload Control System attachment is installed.

The momentary PCS Store Switch provides one switch to ground input to the Implement ECM. The same common ECM ground circuit (C214) is used for the switch that is used for the other Implement ECM connected switches and sensors. The ground circuit is connected to the Implement ECM and the Machine ECM at contact J1-70.

When the Payload Control System feature is active, the PCS Store Switch is used to store the current truck information in the Implement ECM memory. The switch is also used to reset the current truck weight and machine bucket weight to zero.

When the PCS Store Switch is pressed, the ECM will detect that the switch input circuit is grounded. The Implement ECM response will be dependent on the PCS mode that is currently active.

The Implement ECM does not monitor the PCS Store Switch for diagnostics.

Rotary Lift Position Sensor

Illustration 5	g02464057
Rotary Lift Position Sensor

Illustration 6	g02464077

The Rotary Lift Position Sensor provides a PWM input signal to the Implement ECM. The ECM will monitor the duty cycle of each of the PWM input signals.

A specific duty cycle of for each sensor will correlate with a specific position of the lift linkage. The ECM will use this information to determine the position of the implement for control of the implement system and for control of the Payload Control System.

Each position sensor is supplied system voltage through the left column, fuse 2 in the switched upper fuse panel (10A - circuit 146-GY). Each sensor is supplied an ECM ground circuit (C214-BK) connection from the Implement ECM J1-70 contact and the Machine ECM J1-70 contact.

The C214-BK ECM ground circuit is interconnected between the two ECMs. This ground circuit is used for ECM location code ground connections and for ground supply connections. Most of the switches and sensors that are connected to the two ECMs also use this ground circuit.

Each sensor is an identical hall effect sensor that operates at a frequency of 500 ± 100 Hz.

The sensor shaft can mechanically rotate 360 degrees. However, approximately 140 degrees of rotation are used for the 5 percent to 95 percent duty cycle signal.

Mechanical linkage that is bolted to the lift and tilt arms is connected to the sensor shaft. As the implement is lifted, lowered, or tilted, the linkage will rotate the sensor shaft. This movement will change the duty cycle of the PWM input signal.

The following table indicates the PWM duty cycles that the Implement ECM will consider as acceptable calibration limits for the rotary lift position sensor in the indicated positions.

The Implement ECM will activate an FMI 03 (voltage above normal) diagnostic code for a rotary position sensor when the duty cycle is greater than 96.5 percent.

The ECM will activate an FMI 04 (voltage below normal) diagnostic code for a specific rotary position sensor when the duty cycle is less than 3.5 percent.

The rotary position sensors can be calibrated to any position in the acceptable duty cycle range.

If the duty cycle is more than ± 5 percent from the calibrated duty cycle for the Rotary Lift Position Sensor, but is still within the acceptable range, the ECM will activate an FMI 13 (calibrate sensor) diagnostic code.

If the duty cycle is outside of the calibrated value by ± 5 percent, but is still within the acceptable range, the ECM will activate an FMI 13 (calibrate sensor) diagnostic code.

Note: If the attachment Autodig function or the FRAC function is installed on the machine, the acceptable tolerance for calibrated duty cycle is reduced to ± 3 percent.

The Rotary Lift Position Sensor must be "enabled" using Cat ET when the Payload Control System is installed on the machine.

If an abnormal condition is detected in the Lift Position Sensor or the circuits that are used for the sensor, the Implement ECM will activate a CID 350 diagnostic code.

Lift Cylinder Head End Pressure Sensor, Lift Cylinder Head End Pressure Sensor,

Illustration 7	g02464756
Lift cylinder pressure sensor locations (4) Lift Cylinder Head End Pressure Sensor located on the small manifold that is mounted on the underside of the non-engine end frame under the sampling ports on the right side of the machine. View: From the machine left side. In front of the articulation hitch looking toward the right side of the non-engine end frame. (5) Lift Cylinder Rod End Pressure Sensor located on the left side of the Implement Control Valve. View: Non-engine end frame access cover removed, on the left side of the Implement Control valve

The Lift Cylinder Head End (HE) Pressure Sensor is a 50 MPa (7252 psi) rated pressure sensor that operates at approximately 500 Hz. The sensor input is used for automatic downshifts in the Auto 1 to 4 Mode. The sensor input is also used when the Aggregate Autodig attachment is installed on the machine or when the Payload Control attachment is installed on the machine.

The pressure sensor input data is used to determine the force on the work tool when loading in Autodig. The sensor is also used in the machine payload calculation for the Payload Control System.

The Lift Cylinder Rod End (RE) Pressure Sensor is installed on the machine when the Payload Control System attachment is installed on the machine. The sensor is a 50 MPa (7252 psi) rated pressure sensor that operates at approximately 500 Hz. The input signal data from the RE pressure sensor is used along with the input data from the HE sensor data in the machine payload calculation.

Both pressure sensors receive an operating power supply and ground supply from the Implement ECM 8 VDC power supply.

When powered, each pressure sensor will provide a PWM input signal to the Implement ECM. The duty cycle of the PWM input circuit will correlate to a specific oil pressure.

A loss of the operating power or ground circuit will cause an above normal input voltage signal due to the ECM pull voltage.

The pressure sensor PWM duty cycle range that the Implement ECM will consider as acceptable is 5 percent to 95 percent.

The following table indicates the sensor PWM duty cycles at the given oil pressures.

When installed, the lift cylinder pressure sensors are monitored by the Implement ECM for diagnostics. The CID diagnostic codes that are assigned to each pressure sensor are:

• CID 0364 - Lift Cylinder Head Pressure Sensor

• CID 0769 - Lift Cylinder Rod Pressure Sensor

If the PWM duty cycle or voltage of a cylinder pressure sensor input circuit is greater than 97 percent, the Implement ECM will active a diagnostic code with an FMI 03 (voltage above normal).

If the PWM duty cycle or voltage of a cylinder pressure sensor input circuit is less than 3 percent, the Implement ECM will active a diagnostic code with an FMI 04 (voltage below normal).

If the ECM detects that the operating frequency of a cylinder pressure sensor is less than 400 Hz or greater than 600 Hz, the Implement ECM will active a diagnostic code with an FMI 08 (abnormal frequency, pulse width, or period).

For more information on how the Lift Cylinder Head End (HE) Pressure Sensor is used for control of the Autodig feature, refer to Systems Operation, "Aggregate Autodig" in this manual.