Note: If there is a problem with the electrical system for the hoist, the "Chassis Electronic Control Module (ECM)" will cause the modular handle (hoist) valve to remain in the HOLD position until the problem is fixed. When the problem is fixed, the modular handle (hoist) must be placed in the HOLD position. This will reset the "Chassis ECM" allowing normal operation of the valve for the modular handle (hoist).
Check the Modular Handle (Hoist) Lever
- Turn the start switch key to the ON position.
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Illustration 1 g06201777 View of the location for the "Information Touch Screen". The screen display will change when navigating the touch screen.
(1) 459-2222 Display Module Gp
(2) 458-3039 Hoist Control Gp - View the position of the modular handle (hoist) lever on the Information Touch Screen by using Step 4 through Step 2.d.
- Select "Service" from the "Home" menu.
- Select "Service Parameters".
- Select either "Sort by ECM" or "All Parameters".
- View the position of the modular handle (hoist) lever.
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Illustration 2 g06194115 The position of the tuck bed is displayed as an icon on the information screen. - Move the modular handle (hoist) through the four positions RAISE, HOLD, FLOAT, and LOWER.
- Compare the display on the "Advisor" with the position of the modular handle (hoist) lever.
The hoist lever position sensor receives 24 V from the "Chassis ECM". Refer to Step 3 and Step 4 to check the supply voltage to the sensor.
- Remove the cover for the center console.
- Remove the modular handle (hoist) to access the sensor for the modular handle (hoist).
- Connect a multimeter between Pin "A" (battery) and Pin "B" (ground) of the connector that is for the modular handle (hoist) position sensor.
- Set the multimeter to read "DC Volts".
Refer to Step 5 through Step 7 to check the output signal of the modular handle (hoist) position sensor.
- Connect a multimeter between Pin "B" (ground) and Pin "C" (signal) of the connector for the modular handle (hoist) position sensor.
- Set the multimeter to read "Duty Cycle".
- The duty cycle output of the sensor should be approximately 97 percent when the lever is in the full RAISE position. The duty cycle output of the sensor should be approximately 3.5 percent when the lever is in the full LOWER position.
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| Illustration 3 | g06201839 |
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The Hoist Control module is located beneath the cover of the center console. To access the control, the cover must be removed. | |
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| Illustration 4 | g06201809 |
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Hoist Control module and lever handle. | |
Check the Input and Output of the Chassis Electronic Control Module
- Turn the start switch key to the ON position.
- Lower the dump body.
- View of the default screen for the "Information Touch Screen".
- Navigate the touch screen to view the input and output of the Chassis ECM.
Note: When the engine is not operating, the "Chassis ECM" causes the output to the modular handle (hoist) valve to remain in the HOLD position. To override this condition, hold the modular handle (hoist) in the RAISE position for 30 seconds.
- Select "Service" from the "Home" menu.
- Select "Service Parameters".
- Select either "Sort by ECM" or "All Parameters".
- View the input and output of the "Chassis ECM".
- Place the modular handle (hoist) in the RAISE, HOLD, FLOAT, and LOWER positions.
- Compare the messages from the "Advisor" with Table 1.
| modular handle (hoist) lever | ECM Input (Chassis) | ECM Output (Chassis) |
| RAISE | RAISE | RAISE |
| HOLD | HOLD | HOLD |
| FLOAT | FLOAT | SNUB |
| LOWER | LOWER | SNUB |
Check the Proportional Solenoid Valves
Note: Using Cat® ET to test the proportional solenoids on the modular handle (hoist) valve is easier and faster than adjusting the position sensor for the dump body. The procedure that includes adjusting the position sensor for the dump body should only be done when all other test procedures have been completed.
Using Cat® Electronic Technician (Cat® ET)
- Lower the dump body. Stop the engine.
- Connect Cat® ET to the truck.
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Illustration 5 g01553413 View of the hoist control valve
(1) Raise solenoid
(2) Lower solenoid - Install a multimeter in series with proportional solenoid valve (1).
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Illustration 6 g06231493 - Select the "Chassis ECM" and then choose the "Diagnostics" drop-down menu to select "Diagnostic Tests".
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Illustration 7 g06231499 When the new window opens, locate and select "Override Parameters". Show/hide table
Illustration 8 g06231505 - The list of optional "Chassis ECM Overrides" will appear. Select the "Hoist Raise Solenoid Current Override" for proportional solenoid valve (1) and click the "Change" button at the bottom left corner of screen.
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Illustration 9 g06231509 - Enter value 2.000 for the amperes.
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Illustration 10 g06231514 Note: The Lower and Raise overrides cannot be active at the same time. Only one can be overridden at a time.
- The override will take effect and the new value will be displayed in the "Override" screen.
Note: Select the "Hoist Lower Solenoid Current Override" for proportional solenoid valve (2).
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Illustration 11 g06231544 The list of optional "Chassis ECM Overrides" will appear. Select the "Hoist Lower Solenoid Current Override" for proportional solenoid valve (1) and click the "Change" button at the bottom left corner of screen. Show/hide table
Illustration 12 g06231521 Enter the 2.000 value for amperes. Show/hide table
Illustration 13 g06231526 Show/hide table
Illustration 14 g06231530 - The override will take effect and the new value will be displayed in the "Override" screen.
- Disconnect the multimeter and the Cat® ET.
Using the Position Sensor for the Dump Body
- Lower the dump body. Stop the engine.
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Illustration 15 g01622161 View of the hoist control valve
(1) Raise solenoid
(2) Lower solenoid - Install a multimeter in series with proportional solenoid valve (1).
Note: When the engine is not operating, the "Chassis ECM" causes the output to the modular handle (hoist) valve to remain in the HOLD position. To override this condition, hold the modular handle (hoist) in the RAISE position for 30 seconds.
- Move the modular handle (hoist) lever to the RAISE position. Record the reading on the multimeter. Compare the recorded value with the value in Table 2.
- Move the modular handle (hoist) lever to the HOLD position. Record the reading on the multimeter. Compare the recorded value with the value in Table 2.
- Use the message center for the "Information Touch Screen" to view the position of the position sensor for the dump body.
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Illustration 16 g06193913 View of the position sensor for the dump body - Disconnect linkage (1) for the position sensor for the dump body. Move linkage (1) to rotate the position sensor for the dump body to approximately 40 degrees. Verify that the position sensor has been rotated to the second stage of the hoist cylinders on the message center for the "Advisor".
Note: The hoist cylinders must be in the second stage or the dump body must be raised more than 40 degrees for the modular handle (hoist) valve to be in the LOWER position.
- Move the modular handle (hoist) lever to the LOWER position. Record the reading on the multimeter. Compare the recorded value with the value in Table 2.
- Move the modular handle (hoist) to the FLOAT position. Record the reading on the multimeter. Compare the recorded value with the value in Table 2.
- Connect linkage (1) for the position sensor onto the dump body. Check the reading on the multimeter within 20 seconds. Record the reading on the multimeter. The recorded value is for the SNUB position.
Note: After linkage (1) is connected to the dump body, the modular handle (hoist) valve will be in the SNUB position for 20 seconds. After 20 seconds, the modular handle (hoist) valve will change to the low-power FLOAT position. Compare the recorded value with the value in Table 2.
- Disconnect the multimeter.
- Repeat Step 1 through Step 10 for proportional solenoid valve (2).
- Compare the recorded values with the values in Table 2.
Note: The solenoid valves receive a maximum of 1.9 A of current from the Chassis ECM when the proportional solenoid valves are fully activated.
| Modular Handle (Hoist) Lever | Amperes | Solenoid (1) (1) | Solenoid (2) (2) |
| RAISE | 1.9 | High | Off |
| HOLD | 0 | Off | Off |
| FLOAT | 1.56 | Low | Low |
| LOWER | 1.9 | Off | High |
| SNUB | .82 | Low | Low |
| (1) | Raise Solenoid |
| (2) | Lower Solenoid |
Hoist Lower Valve Adjustment Status (Snubbing) - Configure
Modifying the value of the snubbing will alter the time required for the body to drop completely to the frame once snubbing occurs. The snubbing is adjusted through Cat® ET. The configuration value that is changed is the "Hoist Lower Valve Adjustment Status".
To modify the snubbing, perform the following steps using Cat® ET.
- Click "Service" from the top menu and click "Configuration" from the drop-down menu.
- Under "Chassis 785G", select "Hoist System" on the left-side of the screen.
- Select "Hoist Lower Valve Adjustment Status" on the right-side menu and click the "Change" button at the bottom of the screen.
- On the "Change Parameter Value" pop-up box, enter a new value and click "OK". The snubbing value range is "+5" to "-5". Refer to 3.
| Hoist Lower Valve Adjustment Status | |
|---|---|
| Value | Result |
| +5 | Snubbing will occur later or snubbing will occur at a lower angle. The body could hit the rails of the frame with force. |
| 0 | Default value |
| -5 | Snubbing will occur earlier or snubbing will occur at a greater angle. The bed may not sit on the frame. |