LAMP-HEAD 4761865 - Caterpillar

Illustration 1 g00955796
Schematic AP-655C
Illustration 2 g01117365
Schematic AP-1000D, AP-1055DThe parking brake switch has two inputs for the ECM. The inputs are Normally Open or Normally Closed. During normal operation, one of the inputs is open and the other input is grounded. A failure is detected when the Normally Open input and the Normally Closed input are in the same state. This diagnostic code is recorded when the Normally Open input and the Normally Closed input are in the same state. The possible causes of the problem are listed below:
There is an open or grounded wire between 419-YL and the ECM.
There is an open wire or a grounded wire between A314-OR and the ECM.
One or more of the parking brake switches have failed.
There is an open on wire A275-BK.
The ECM has failed. ECM failure is unlikely. System Response:
The machine will not move.
The fault lamp for the propulsion system is ON.
The action alarm and action lamp is ON.Test Step 1. CHECK THE CIRCUIT FOR THE PARKING BRAKE SWITCH
Turn the disconnect switch (if equipped) and the key start switch to the OFF position.
Disconnect the J1 connector from the ECM.
Ensure that all of the parking brake switches are released.
Measure the resistance between contact J1-12 and contact J1-44.
Measure the resistance between contact J1-12 and contact J1-57. Expected Result:The resistance measurement between contacts J1-12 (wire A275-BK) and J1-44 (wire 419-YL) is greater than 5000 ohms. The resistance between contacts J1-12 (wire A275-BK) and J1-57 (wire 419-YL) should be less than 5 ohms.Note: The resistance measurements should be reversed when the status of the parking brake switch is changed.Results:
OK - The resistance measurement between contacts J1-12 (wire A275-BK) and J1-44 (wire 419-YL) is greater than 5000 ohms. The resistance between contacts J1-12 (wire A275-BK) and J1-57 (wire 419-YL) should be less than 5 ohms. The ECM has failed.Repair: ECM failure is unlikely. Exit this procedure and perform this procedure again. If the cause of the failure is not found, replace the ECM. See the Testing and Adjusting, "Electronic Control Module (ECM) - Replace" section of this manual.STOP
NOT OK - The resistance between contacts J1-12 and J1-44 is NOT greater than 5000 ohms. The resistance between contacts J1-12 and J1-57 is NOT less than 5 ohms. Proceed to test step 2.Test Step 2. CHECK THE HARNESSNote: This Test Step is performed for both operator stations.
The J1 harness connector remains disconnected from the ECM.
Install a jumper between contacts 3 (wire A275-BK) and 4 (wire 419-YL) at the switch.
Measure the resistance between contacts J1-12 (wire A275-BK) and J1-44 (wire 419-YL) of the machine harness connector for the ECM. Make a note of the resistance measurement.
Remove the jumper from contact 4 (wire 419-YL) and place the jumper on contact 1 (wire A314-OR) at the switch.
Measure the resistance between contacts J1-12 (wire A275-BK) and J1-57 (wire A314-OR) of the machine harness connector for the ECM. Make a note of the resistance measurement.Expected Result:The resistance is less than 5 ohms for each measurement.Results:
OK - The resistance is less than 5 ohms. The harness is