826G Landfill Compactor, 825G Soil Compactor, 824G Wheel Dozer and 980G Wheel Loader Power Train Electronic Control System Caterpillar

Illustration 1	g00775678
Schematic for the Pressure Switch (Parking Brake Oil)

This diagnostic code is recorded when the status of both the N/O and N/C switch inputs of the power train ECM are grounded. The switch has a N/O input and a N/C input. These two inputs are connected to the power train ECM. During proper operation, one of the inputs is open and the other input is grounded.

Possible causes of this diagnostic code are listed:

• The harness has failed.

• The switch has failed.

System Response:

The machine response is listed:

• The operator retains all functions of the transmission control.

• Drive through protection can not be invoked.

Note: This procedure can cause new diagnostic codes to be recorded. Ignore these created diagnostic codes. Complete the following procedure. Then clear the created diagnostic codes.

Note: Ensure that the diagnostic code is active and that the diagnostic code indicator is active.

Test Step 1. Check the Switch.

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

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

Expected Result:

The diagnostic code indicator should remain active.

Results:

• YES - The diagnostic code indicator remains active. Proceed to test step 2.

• NO - The diagnostic code indicator is inactive.

  Repair: Repeat the previous test step in order to verify that the switch has failed. Repair the switch and/or the harness or replace the switch and/or the harness.

  Stop.

Test Step 2. Check the Harness Circuit.

This step checks the continuity of the entire harness circuit that has failed. The switch that was checked in the previous test step is rechecked in this step.

1. Turn the disconnect switch to OFF position.

2. Connect the switch from the previous step.

3. Disconnect the harness from the power train ECM.

4. At the harness connector for the power train ECM, check the continuity to ground of the N/C contact and the N/O contact. Check the continuity of both contacts while the switch is activated and deactivated. Refer to Table 1.

Expected Result:

The continuity check should agree with the table.

Results:

• YES - The continuity check agrees with the table.

  Repair: It is unlikely that the ECM has failed. Perform the previous steps again. If the cause is not found, replace the power train ECM. Refer to Testing and Adjusting, "Electronic Control Module (Power Train) - Replace".

  Stop.

• NO - The continuity check does not agree with the table.

  Repair: There is a short to ground in the harness between the power train ECM and the switch. Repair the harness or replace the harness.

  Stop.