The auxiliary control sends a proportional signal to the ECM. The signal is a pulse width modulated signal that is generated at a frequency of 500 ± 80 Hz. When the auxiliary control is in the neutral position, a duty cycle of 50% ± 3% is seen by the ECM. When the auxiliary control is moved upward from the neutral position, the duty cycle will vary from 50% to 20%. When the auxiliary control is moved downward from the neutral position, the duty will vary from 50% to 80%. The ECM receives the proportional signals and the ECM will send a proportional signal to the corresponding modulated valve (auxiliary) (No. 1 or No. 2). The ECM monitors the auxiliary control for duty cycles that are out of range. A diagnostic code will then be set.
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| Illustration 1 | g01045031 |
Schematic for the auxiliary hydraulic circuit | |
Note: Check for any diagnostic codes that are displayed on the Caterpillar ET before performing the following test steps.
Test Step 1. CHECK FOR PROPER OPERATION
- Run the machine.
- Actuate the auxiliary control upward from the NEUTRAL position and operate the auxiliary control downward from the NEUTRAL position.
Expected Result:
The auxiliary control should have operated the auxiliary hydraulics.
Results:
- OK - The auxiliary control operates the auxiliary hydraulics.
Repair: There is no problem at this time.
Stop.
- NOT OK - The auxiliary control did not operate the auxiliary hydraulics. Proceed to Test Step 2.
Test Step 2. CHECK THE STATUS OF THE AUXILIARY CONTROL
- Turn the key start switch to the OFF position.
- Turn the key start switch to the ON position.
- Check the status of the auxiliary control on the Caterpillar ET.
Expected Result:
The status of the "Auxiliary Hydraulics Lever" should display 0%.
Results:
- OK - The status of the "Auxiliary Hydraulics Lever" displays 0%. Proceed to Test Step 3.
- NOT OK - The status of the "Auxiliary Hydraulics Lever" does not display 0%.
Repair: See Troubleshooting, "Position Sensor (Auxiliary Control)".
Stop.
Test Step 3. CHECK THE STATUS OF THE AUXILIARY CONTROL
- Actuate the auxiliary control downward and observe the status on the Caterpillar ET.
- Actuate the auxiliary control upward and observe the status on the Caterpillar ET.
Expected Result:
The "Auxiliary Hydraulics Lever" status should have changed from "-100%" to "100%" approximately.
Results:
- OK - The "Auxiliary Hydraulics Lever" status changed from "-100%" to "100%" approximately. Proceed to Test Step 4.
- NOT OK - The "Auxiliary Hydraulics Lever" status did not change from "-100%" to "100%" approximately.
Repair: See Troubleshooting, "Position Sensor (Auxiliary Control)".
Stop.
Test Step 4. CHECK FOR DIAGNOSTIC CODES
- Check the Caterpillar ET for any diagnostic codes.
Expected Result:
No diagnostic codes should be present.
Results:
- OK - No diagnostic codes are present.
Repair: Check the system hydraulics. See Testing and Adjusting, RENR3584.
Stop.
- NOT OK - Diagnostic codes are present.
Repair: See the troubleshooting section of this manual for the diagnostic code.
Stop.