D6N Track-Type Tractor Caterpillar

Illustration 1	g02686776
Winch Control switch connections

A CID 3784is associated with the Winch Control switch. An FMI 04 indicates the Machine ECM has determined the voltage in the switch circuit is below normal.

Possible causes for this diagnostic code are:

• The switch has failed.

• The switch circuit is open.

• The switch circuit is shorted to a +VDC source.

• Machine ECM has failed. ECM failure is unlikely.

Note: Poor connections are often the cause of a problem in electrical circuits. Before performing this procedure, inspect all the machine harnesses and connectors involved in the circuit. Make sure to verify that all of the connections in the circuit are clean, secure, and in good condition. Correct any problems found with any of the connections. Verify the diagnostic code CID 3784 FMI 04 is still active, before continuing with this procedure.

Note: The following test procedure may create other diagnostic codes. Ignore all the created diagnostic codes now, but clear all those codes after the cause for the original diagnostic code has been corrected.

Test Step 1. CHECK THE SWITCH OPERATION

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

2. Disconnect the Winch Mode Switch from the harness connector.

3. At the Winch Mode Switch connector, measure resistance from contact 4 to contact 6 while toggling the Winch Control switch to the N/C Brake Mode and N/O Free Spool positions.

Expected Result:

The meter shows the Winch Control switch contacts both open and close, as the switch is toggled.

Results:

• YES - The Winch Control switch continuity checks are correct. The switch is working correctly. Go to Test Step 2.

• NO - The Winch Control switch continuity checks are not correct. The switch is not working correctly.

  Repair: Replace the switch.

  Go to Test Step 4.

Test Step 2. CHECK THE SWITCH CIRCUIT FOR AN OPEN OR POOR CONNECTION.

1. The disconnect switch and the key switch remain in the OFF position.

2. The Winch Mode Switch handle harness connector remains disconnected.

3. At the harness connector for the switch, connect a jumper wire from contact 4 (wire P775-BU) to contact 6 (wire P776-GN).

4. Disconnect the J2 harness connector from the machine ECM.

5. At the ECM harness connectors, measure the resistance from contact J2-61 (wire P775-BU and contact J2-62 (wire P776-GN).

6. While observing the resistance measurement of the circuits, gently wiggle the machine harness near the ECM connectors and near the switch connector. Do not disconnect the jumper wire.

Expected Result:

The resistance measurement is less than 5 ohms at all times during the manipulation of the harness.

Results:

• OK - The resistance measurement stayed less than 5 ohms at all times. There are no open circuits or poor connections in the harness. Go to Test Step 3.

• NOT OK - A resistance measurement read greater than 5 ohms during the measurement. There is an open or poor connection in one or both the sensor circuit wires.

  Repair: Check the end to end continuity of each sensor circuit individually, to determine which circuit has the open or poor connection.Repair or replace the harness.

  Go to Test Step 4.

Test Step 3. CHECK THE SWITCH CIRCUITS FOR A SHORT TO A +VDC SOURCE IN THE HARNESS.

1. The disconnect switch and the key switch remain in the OFF position.

2. The Winch Mode Switch connector remains disconnected.

3. Disconnect the J2 harness connector from the Machine ECM.

4. At the J2 ECM harness connector, measure resistance between the N/O switch contact J2-62 (wire P776-GN) and frame ground.

5. At the J2 ECM harness connector, measure resistance between the N/C switch contact J2-61 (wire P775-BU) and frame ground.

Expected Result:

Each resistance measurement should be greater than 5000 ohms.

Results:

• OK - Each resistance measurement is greater than 5000 ohms. There are not short circuits in the harness. Go to Test Step 4.

• NOT OK - One or more of the resistance measurements are less than 5 ohms. There is a short circuit in the harness.

  Repair: The short is between the two circuits that registered the low resistance.Repair or replace the harness.

  Go to Test Step 4.

Test Step 4. CHECK THE DIAGNOSTIC CODE STATUS.

1. Reconnect the machine harness connectors. Ensure that all the connectors are clean, and fully seated. Observe that the clips for each connector are securely fastened.

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

3. Clear all inactive diagnostic codes.

4. Operate the machine.

5. Check the status of the CID 3784 FMI 04 diagnostic code.

Expected Result:

The diagnostic code is not active.

Results:

• OK - The diagnostic code is no longer active and does not exist at this time.

  Repair: Return machine to normal operation.

  STOP

• NOT OK - The diagnostic code is still active. The problem has not been corrected. The ECM may have failed.

  Repair: Perform a 45 N (10 lb.) pull test on each of the wires that are associated with the sensor circuit.Perform a "wiggle test" on the switch circuit of the machine wiring harness, using the Caterpillar Electronic Technician service tool. The "wiggle test" may be used to detect open or shorted connections in the machine wiring harness.Reconnect all harness connectors. Ensure that the connectors are seated. Observe that the clips for each connector are fastened. If the problem was again not found, and the original code is still active, the machine ECM may have failed.Prior to replacing an ECM, always contact your Dealership Technical Communicator for possible consultation with Caterpillar, or with the Dealer Solutions Network. This consultation may greatly reduce repair time. If the ECM needs to be replaced, refer toTesting and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP