GUARD AS 3W8396 - Caterpillar

Illustration 1 g00777327
The 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 A315-WH and the ECM.
There is an open wire or a grounded wire between A314-OR and the ECM.
The parking brake switch has failed.
The ECM has failed. This is unlikely. System Response:The 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.
Measure the resistance between contact J1-12 and contact J1-44.
Measure the resistance between contact J1-12 and contact J1-54. Expected Result:The resistance measurement between contacts J1-12 (wire J764-BR) and J1-44 (wire A315-WH) is greater than 5000 ohms. The resistance between contacts J1-12 (wire J764-BR) and J1-54 (wire A314-OR) should be less than 5 ohms.Note: The resistance measurements should be reversed when the status of the park brake switch is changed.Results:
OK - The resistance measurement between contacts J1-12 (wire J764-BR) and J1-44 (wire A315-WH)is greater than 5000 ohms. The resistance between contacts J1-12 (wire J764-BR) and J1-54 (wire A314-OR) should be less than 5 ohms. The ECM has failed.Repair: It is unlikely that the ECM has failed. 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 J1-54 is NOT less than 5 ohms. Proceed to test step 2.Test Step 2. CHECK THE HARNESS
The J1 harness connector remains disconnected from the ECM.
Install a jumper between contacts 2 (wire J764-BR) and 3 (wire A315-WH) at the switch.
Measure the resistance between contacts J1-12 (wire J764-BR) and J1-44 (wire A315-WH) of the machine harness connector for the ECM. Make a note of the resistance measurement.
Remove the jumper from contact 3 (wire A315-WH) and place the jumper on contact 1 (wire A314-OR) at the switch.
Measure the resistance between contacts J1-12 (wire J764-BR) and J1-54 (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 correct.Repair: Replace the switch.STOP
NOT OK - The resistance is greater than 5 ohms for one or both of the measurements. The harness has failed.Repair: Repair the machine harness or replace the machine harness.STOP