621H, 623H and 627H Wheel Tractor-Scrapers Implement Electronic Control System Caterpillar

This procedure is used when a calibration of the joystick fails. The procedure assumes that the Electronic Technician (ET) is ON after a failed calibration.

Test Step 1. CHECK THE ERROR MESSAGE.

1. Check the error message on the ET screen.

Expected Result:

There is an error message.

Results:

• Active diagnostic present - The error message on the ET screen is "Active diagnostic present". Proceed to Test Step 2.

• Calibration value too large - The error message on the ET screen is "Calibration value too large". Proceed to Test Step 4.

• Calibration value too low - The error message on the ET screen is "Calibration value too low". Proceed to Test Step 4.

Test Step 2. CHECK FOR DIAGNOSTIC CODES.

1. Use the ET in order to check for diagnostic codes.

Expected Result:

There are no diagnostic codes that are present.

Results:

• YES - There are no diagnostic codes that are present. Proceed to Test Step 3.

• NO - Diagnostic codes are present.

  Repair: Refer to the appropriate diagnostic code procedure. See Troubleshooting, "Diagnostic Code List".

  STOP

Test Step 3. INSPECT THE HARNESS CONNECTIONS.

1. Turn the disconnect switch to the OFF position.

2. Inspect all of the harness connections that are related to the circuit for the calibration pressure switch. Make sure that the connectors are clean and tight.

3. Check the connectors for proper mating. Ensure that all the seals are present and in place.

4. Check the harness for signs of damage or abrasion.

5. Check the wires at the connector. Ensure that the wires are secured tightly into the connector. Take care not to pull the wire out of the connector.

6. Check the exposed wires at the connectors for nicks or signs of abrasion.

7. Check for moisture inside the connector.

8. Check the connectors for dirty contacts or corroded contacts.

9. Check each pin and each socket of the machine harness connectors. Ensure that the contacts are properly installed. The contacts should mate correctly when the two pieces of the connector are placed together.

Expected Result:

The machine harness connectors are tight and free of corrosion.

Results:

• OK - The machine harness connectors are tight and free of corrosion. Proceed to Test Step 4.

• NOT OK - The machine harness connectors are in need of repair.

  Repair: Repair the machine harness or replace the machine harness.

  STOP

Test Step 4. CHECK THE JOYSTICK.

1. Check that the joystick is held in the proper position during the calibration.

Expected Result:

The joystick was held in the proper position during the calibration procedure.

Results:

• YES - The joystick was held in the proper position during the calibration procedure and the calibration still failed. Proceed to Test Step 5.

• NO - The joystick was not held in the proper position. After attempting the calibration again, the calibration was successful.STOP

Test Step 5. CHECK THE SIGNALS FROM THE JOYSTICK DURING THE CALIBRATION.

For this check, proceed to the proper calibration procedure and recalibrate the joystick. During the calibration, check the duty cycle of the signals that are coming from the joystick. Refer to Testing and Adjusting, "Implement Control Lever - Calibrate"

1. At the harness connector for the joystick, connect the positive lead from the multimeter to the signal contact. Connect the negative lead from the multimeter to the ground contact. The contacts and wire numbers are listed in table 1.
   Show/hide table

   Table 1

   Calibration Information For The Joystick
   Function	Positive Lead Of The Multimeter	Negative Lead Of The Multimeter
   Bowl	6-pin connector (Joystick) contact 5 wire R752-YL	6-pin connector (Joystick) contact 2 wire 299-BK
   Ejector	6-pin connector (Joystick) contact 3 wire R750-GN	6-pin connector (Joystick) contact 2 wire 299-BK
   Apron or Elevator	main 12-pin connector (Joystick) contact 3 wire R749-BU	main 12-pin connector (Joystick) contact 2 wire P770-WH

2. Set the multimeter to the setting for "PWM%".

3. Perform the calibration for the joystick. As you perform the calibration, note the duty cycle on the multimeter. The proper values are shown in table 2.
   Show/hide table

   Table 2

   Joystick Calibration Duty Cycle Values
   Position of the Joystick	Minimum Duty Cycle (%)	Maximum Duty Cycle (%)
   Joystick Rearward	7	13
   Joystick Neutral	45	55
   Joystick Forward	87	93
   Joystick Left	7	13
   Joystick Neutral	45	55
   Joystick Right	87	93
   Thumb Roller	15	25
   Thumb Roller Neutral	45	55
   Thumb Roller	75	85

Expected Result:

The values for the duty cycle are in the appropriate range.

Results:

• YES - The values for the duty cycle are in the appropriate range. The calibration of the joystick was successful. Perform any other calibrations of the solenoids that are necessary. Resume normal machine operation.STOP

• NO - The values for the duty cycle are not in the appropriate range. Recalibration of the joystick was not successful.

  Repair: The joystick has an internal failure. The joystick has serviceable parts. Replace the parts that are suspected of causing the problem.

  STOP