279C, 279C2, 289C, 289C2 and 299C Compact Track Loaders, 287C, 277C, 277C2, 287C2 and 297C Multi Terrain Loaders and 246C, 256C, 262C, 262C2 and 272C Skid Steer Loaders Machine Electronic Control System Caterpillar

Illustration 1	g01269997
Schematic of the Pattern Change Switch Circuit

This diagnostic code is associated with the Pattern Change Switch. This diagnostic code is recorded when the status of both the normally open inputs and the normally closed input are grounded. This switch has three inputs to the ECM. Two inputs are normally open and one is normally closed. During proper operation in one held switch position, one normally open contact will be closed and the other normally open contact will remain open. When the switch is actuated to the opposite position, the first contact will now be open and the other normally open contact will now be closed.

The possible causes of this diagnostic code are listed:

• A normally open circuit is shorted to ground while the normally closed circuit is grounded through the switch.

• The normally closed circuit is shorted to ground while the normally open circuit is grounded through the switch.

• The normally open circuits and the normally closed circuits are shorted to ground in the harness.

• The normally open circuits and normally closed circuits are shorted together. The switch must be in one specific position.

• The switch has failed.

System Response:

If the switch is faulted during operation, the last known value will be saved. If the switch is faulted at power up, the park brake will remain engaged and the implements will be locked out.

Table 1 contains wire numbers and connector contacts. Use this information to troubleshoot the failed circuit.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the original diagnostic code is corrected.

Ensure that the diagnostic code is active.

Test Step 1. CHECK THE SWITCH.

1. Observe ON/OFF status of the diagnostic code indicator.

2. Disconnect the connector of the switch from the harness.

Expected Result:

The diagnostic code remains active.

Results:

• YES - The diagnostic code remains active. The switch is not the cause of the diagnostic code. Proceed to test step 2 .

• NO - The diagnostic code is inactive. The switch has failed or the harness has failed.

  Repair: Repeat this test in order to verify the failure of the switch. Repair the switch or replace the switch. Repair the harness or replace the harness.

  STOP

Test Step 2. CHECK THE HARNESS CIRCUIT.

1. This test checks the continuity of the entire harness circuit that has failed. This test includes the switch that was previously checked.

2. Reconnect the switch that was disconnected in the previous step.

3. Disconnect the harness from the ECM.

4. Activate the switch in one direction. At the harness connector for the ECM, check the continuity to ground of the normally closed contact and the normally open contact.

5. Activate the switch in the opposite direction. At the harness connector for the ECM, check the continuity to ground of the normally closed contact and the normally open contact.

Expected Result:

The continuity agrees with table 1.

Results:

• YES - The continuity agrees with the values in the preceding table. The harness circuit is correct.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this troubleshooting procedure again. 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 must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP

• NO - The continuity check DOES NOT agree with values in the preceding table.

  Repair: The harness circuit has failed. There is a short to ground in the harness between the ECM and the switch. Repair the harness or replace the harness.

  STOP