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 both switch circuits are grounded, the ECM will disable implement control. The ECM will activate a CID 0490 FMI 03 diagnostic code, in this case ground, above normal.

The possible causes of this diagnostic code are listed below:

• The switch has failed.

• One or both of the switch circuits have an open or poor connection.

• There is a short to a voltage source in one or both of the switch circuits.

• 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 switch connector 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 03 diagnostic code remains the same when the switch is disconnected.

Results:

• OK - The CID 0490 FMI 03 diagnostic code remains the same. Proceed to Test Step 2.

• NOT OK - The CID 0490 FMI 03 diagnostic code is NO longer active. A CID 0490 FMI 04 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 FOR AN OPEN IN THE SWITCH CIRCUITS

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

2. Disconnect the machine harness connector from the lockout switch.

3. At harness connector for the switch, place a jumper wire between the switch contact 1 (wire E918-GN) and frame ground.

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

5. Observe the status of the active CID 0490 FMI 03 diagnostic code.

6. At harness connector for the switch, place a jumper wire between the switch contact 3 (wire E917-WH) and frame ground.

7. Observe the status of the active CID 0490 FMI 03 diagnostic code.

Expected Result:

The active diagnostic code CID 0490 FMI 03 is no longer active. A CID 0490 FMI 04 diagnostic code becomes active when the switch circuit (E918-GN) or (E917-WH is grounded.

Results:

• YES - The active diagnostic code CID 0490 FMI 03 is no longer active. A CID 0490 FMI 04 diagnostic code has been activated after the switch circuit is grounded. Proceed to Test Step 3.

• NO - The CID 0490 FMI 03 diagnostic code remains active. The status of the active diagnostic code does not change when the switch circuit is grounded. There is an open or a poor connection in the switch circuit.

  Repair: Check the switch circuit for an open or for a poor connection. Repair or replace the machine harness.

  STOP

Test Step 3. CHECK FOR A SHORT TO ANOTHER VOLTAGE SOURCE

The key start switch and the disconnect switch remain in the OFF position. The machine harness remains disconnected from the switch.

1. At the machine harness connector for the switch, place a jumper wire between contact 1 (wire E918-GN) and contact 3 (wire E917-WH).

2. Disconnect the machine harness connectors J1 and J2 from the ECM.

3. At the machine harness connector of the ECM J2, measure the resistance between input contact of the switch J2-31 (wire E918-GN) and each of the other J1 and J2 contacts that are used for the Implement ECM.

4. While the resistance measurement is observed, wiggle the wires and move the machine harness at the ECM connectors and at the connectors for the switch.

5. At the machine harness connector of the ECM J2, measure the resistance between input contact of the switch J2-30 (wire E917-WH) and each of the other J1 and J2 contacts that are used for the ECM.

6. While the resistance measurement is observed, wiggle the wires and move the machine harness at the ECM connectors and at the connectors for the switch.

Expected Result:

Each resistance measurement is greater than 5000 ohms at all times during the manipulation of the wires and connectors of the machine harness.

Results:

• OK - Each resistance measurement is greater than 5000 ohms. The machine harness is not indicating a short. Proceed to Test Step 4.

• NOT OK - Each resistance measurement is not greater than 5000 ohms. There is a short in the machine harness. The short is between the switch circuit E918-GN and the circuit with the low resistance measurement. The short could also be between the switch circuit E917-WH and the circuit with the low resistance measurement.

  Repair: Refer to the complete Electrical System Schematic of the machine. Examine all of the connectors in the faulty circuit for shorts in the machine harness.For information on testing for short circuits and finding short circuits, refer to Testing and Adjusting, "Wiring Harness (Short Circuit) - Test". Repair the machine harness or replace the machine harness.

  STOP

Test Step 4. 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 sensor 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 03 diagnostic code.

Expected Result:

The CID 0490 FMI 03 diagnostic code is not active.

Results:

• OK - The CID 0490 FMI 03 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 03 diagnostic code is still active. The diagnostic code has not been corrected.

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

  • Momentary shorts

  • Intermittent 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