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

This procedure is used when the quick drop function for the bowl does not operate and there are no active diagnostic codes.

Note: The bowl quick drop function is available on 621H and 627H models only.

Test Step 1. CHECK THE CURRENT AT THE BOWL DOWN SOLENOID

Note: Cat^® ET can be used to measure current at the solenoids. This procedure describes the use of the multimeter and AC current probe.

1. Stop the machine and turn the key start switch to the OFF.

2. At the bowl down solenoid, connect the 349-4199 AC/DC Current Probe around wire R716-PK. Connect the leads from the current probe to the multimeter.

3. Turn the key start switch ON. Do not start the engine.

4. Move the joystick to the position for bowl quick drop.
   Reference:
   Operation and Maintenance Manual, "Bowl Control (Joystick)"

5. Measure the current to the bowl down solenoid.

Expected Result:

The current at the bowl down solenoid is above 1.3 A.

Results:

• YES - The current at the bowl down solenoid is above 1.3 A.
  A hydraulic problem is likely.

  Repair: Diagnose the hydraulic problem and correct the problem. Refer to Testing and Adjusting, KENR8874, " 621H, 623H, and 627H Hydraulic and Steering Systems", "Troubleshooting".

  STOP

• NO - The current at the bowl down solenoid is below 1.3 A. Proceed to Test Step 2.

Test Step 2. CHECK THE RESISTANCE OF THE BOWL DOWN SOLENOID

1. Disconnect the machine harness connector from the solenoid.

2. At the solenoid, measure the resistance from contact 1 to contact 2.

Expected Result:

The resistance is approximately 5 ohms.

Results:

• OK - The resistance is approximately 5 ohms. Proceed to Test Step 3.

• NOT OK - The resistance is not approximately 5 ohms.

  Repair: Replace the solenoid.

  STOP

Test Step 3. CHECK THE WIRING HARNESS

1. Turn the key start switch and the disconnect switch to the OFF position.

2. Disconnect the machine harness connector J1 from the ECM.

3. At the bowl down solenoids, disconnect the machine harness connectors from the solenoids. Connect a jumper wire across the two terminals of each wiring harness connector.

4. At the Implement ECM, measure and note the resistance from contact J1-49 (wire R716-PK) to contact J1-50 (wire H801-PU). Measure and note the resistance from contact J1-62 (wire R801-BU) to contact J1-60 (wire H802-GY).

Expected Result:

The resistance measurement is less than 5 ohms.

Results:

• YES - The resistance is less than 5 ohms. The wiring is correct.

  Repair: Recalibrate the joystick. See Testing and Adjusting, "Implement Control Lever (Joystick) - Calibrate".
  If the problem remains after the calibration, the ECM may have failed. ECM failure is unlikely. Perform this entire procedure again.
  If the problem remains, the Transmission/Chassis ECM may have failed. If the ECM requires replacement, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP

• NO - The resistance measurement is greater than 5000 ohms.

  Repair: The wiring harness has failed between the ECM and the bowl down solenoid. Repair or replace the wiring harness.

  STOP