NUT-INSERT 3808803 - Caterpillar

Illustration 1 g01432785
Connections of the auto carry switch
This diagnostic code is associated with the auto carry switch. The FMI 04 is recorded when the ECM determines that the voltage is below normal for the circuit. The switch has three inputs to the ECM. Two of the inputs are normally open and normally closed. During normal operation, one of the inputs is open. The other input is grounded. When a circuit is measured with a voltmeter, an open circuit will measure approximately 10 DCV to ground and a closed circuit will measure approximately 0 DCV to ground. The diagnostic code is recorded when both of the inputs are grounded.The possible causes of this diagnostic code are listed below:
The "normally open" signal circuit (wire C975-WH(White)) is always shorted to ground.
The "normally closed" signal circuit (wire C978-BR(Brown)) is always shorted to ground.
The switch has failed.
The ECM has failed. This is unlikely. Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all of the connections in the circuit are clean and secure. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear these diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 1873 FMI 04 is active before performing this procedure.
Table 1
Status of the Switch
Switch Position J2-39
C975-WH(White) Circuit J2-38
C9778-BR(Brown) Circuit
Up open closed
Down closed open Test Step 1. CHECK THE SWITCH
Check for continuity between contact 1 and contact 2 of the switch.
Press the switch. Release the switch and check for continuity.
Check for continuity between contact 2 and contact 3 of the switch.
Press the switch. Release the switch and check for continuity. Expected Result:The continuity check agrees with Table 1.Results:
OK - The continuity check agrees. Proceed to Test Step 2.
NOT OK - The continuity check does not agree. The switch has failed.Repair: Replace the switch. Verify that the new switch corrects the diagnostic code.STOPTest Step 2. CHECK THE SIGNAL CIRCUITS FOR A SHORT TO GROUND
Reconnect the switch to the machine harness.
The machine harness connectors remain disconnected from the ECM.
At the machine harness connector for the ECM, check for continuity between contact J2-39 (wire C975-WH(White)) and frame ground.
Press the switch. Release the switch and check for continuity.
At the machine harness connector for the ECM, check for continuity between contact J2-38 (wire C978-BR(Brown)) and frame ground.
Press the switch. Release the switch and check for continuity. Expected Result:The continuity check agrees with Table 1.Results:
OK - The continuity check agrees.Repair: If the cause of the problem is not found, contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".STOP
NOT OK - The continuity check does not agree. There is a short in