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

Illustration 1	g02560041
Connections of the implement (Hydraulic) lockout switch

The Implement Lockout Switch provides two "switch to ground" inputs to the Implement ECM. The common ground circuit J765-BU for the switch is provided from the Implement ECM and the Machine ECM.

If the ECM detects that neither switch circuit is grounded, the ECM will disable implement control. The ECM will activate a CID 0490 FMI 04 diagnostic code for voltage, in this case ground, below normal.

The possible causes of this diagnostic code are listed below:

• The switch has failed.

• One or both of the switch inputs is shorted to ground.

• The ECM has failed. This condition is unlikely.

Note: Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, that all connections are secure and that all connections are in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.

Test Step 1. CHECK THE SWITCH

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

2. Ensure that the diagnostic code is active.

3. Observe the status of the diagnostic code while the connector of the switch is disconnected from the machine harness. Reconnect the switch and disconnect the switch again. Observe the status of the diagnostic code.

Expected Result:

The active CID 0490 FMI 04 diagnostic code remains the same when the switch is disconnected.

Results:

• OK - The CID 0490 FMI 04 diagnostic code remains the same. Proceed to Test Step 2.

• NOT OK - The CID 0490 FMI 04 diagnostic code is NO longer active. A CID 0490 FMI 03 diagnostic code becomes active when the connector of the switch is disconnected. The machine harness and the ECM are operating correctly. The switch has failed.

  Repair: Replace the switch. After replacement of the switch, verify that the operation of the new switch is correct before operating the machine.

  STOP

Test Step 2. CHECK THE SWITCH CIRCUITS FOR A SHORT TO GROUND

1. Turn the key start switch and the disconnect switch to the OFF position. The implement lockout switch remains disconnected from the machine harness.

2. Disconnect the J2 machine harness connector from the Implement ECM.

3. At machine harness connector J2 for the Implement ECM, perform the following:
   • Measure the resistance between contact J2-30 (wire E917-WH) and frame ground.

   • Measure the resistance between contact J2-30 (wire E917-WH) and each of the other circuits that are used for the Implement ECM.

4. At machine harness connector J2 for the Implement ECM, perform the following:
   • Measure the resistance between contact J2-31 (wire E918-GN) and frame ground.

   • Measure the resistance between contact J2-31 (wire E918-GN) and each of the other circuits that are used for the Implement ECM.

Expected Result:

Each measurement is greater than 5000 ohms.

Results:

• OK - Each measurement is greater than 5000 ohms. The resistance of the switch circuit does not indicate a short in the machine harness. Proceed to Test Step 3.

• NOT OK - One or more resistances are less than 5000 ohms.

  Repair: There is a short in the machine harness. The short is between the switch circuit and the frame ground. The short could also be between the switch circuit and the circuit that measured low resistance.Refer to the Electrical System Schematic of the machine. Check all of the connectors that are in the switch circuit. Inspect the connections for the following:

  • Connections are clean.

  • Connections are secure.

  • Connections are in good condition.

  For information on testing for short circuits and finding short circuits, refer to the Testing and Adjusting, "Wiring Harness (Short Circuit) - Test" Story in this manual. Repair the machine harness or replace the machine harness.

  STOP

Test Step 3. CHECK THE STATUS OF THE DIAGNOSTIC CODE

1. Inspect the harness connectors. Clean the contacts of the harness connectors. Check the wires for damage to the insulation that can be caused by excessive heat, battery acid, or chafing.

2. Perform a 45 N (10 lb) pull test at the connectors that are used in the switch circuit.

3. Reconnect all harness connectors. Make sure that the connectors are fully seated and locked.

4. Turn the disconnect switch and the key start switch to the ON position.

5. Check the status of the CID 0490 FMI 04 diagnostic code.

Expected Result:

The CID 0490 FMI 04 diagnostic code is not active.

Results:

• OK - The CID 0490 FMI 04 is not active. The diagnostic code does not exist at this time.

  Repair: The initial diagnostic code could have been caused by a poor electrical connection or short at a harness connector that was disconnected and reconnected. Resume normal machine operation.

  STOP

• NOT OK - The CID 0490 FMI 04 diagnostic code is still active. The diagnostic code has not been corrected.

  Repair: If available, perform a Wiggle Test on the wiring harness of the machine with the Caterpillar Electronic Technician (Cat ET) service tool. The Wiggle Test can detect the following in the machine wiring harness:

  • Momentary shorts

  • Opens

  It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, the ECM may have failed. Prior to replacing an ECM, always contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace" section of this manual for additional information.

  STOP