ELECTRONICS GP 2084833 - Caterpillar

Illustration 1 g00820843
Schematic of the Rotary Switch (Variable Shift Control)This diagnostic code is associated with the Rotary Switch (Variable Shift Control). The switch is connected to three inputs of the ECM. Two of the inputs are open and the other input is grounded during proper operation.The FMI 04 means that the ECM has determined that two or more circuits are grounded.Note: The following test procedure may create other diagnostic codes. Ignore these diagnostic codes and clear these diagnostic codes when the original diagnostic code has been corrected.Ensure that the diagnostic code of CID 1521 FMI 04 is active before performing this procedure.Test Step 1. CHECK THE SWITCH
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness from the switch.
Turn the key start switch and the disconnect switch to the ON position.Expected Result:The CID 1521 FMI 04 has been replaced by CID 1521 FMI 03.Results:
OK - The CID 1521 FMI 04 has been replaced by CID 1521 FMI 03. The machine harness and the ECM are correct. Proceed to Test Step 3.
NOT OK - The CID 1521 FMI 04 is still active. Proceed to Test Step 2.Test Step 2. CHECK THE HARNESS
Turn the disconnect switch and the key start switch to the OFF position.
The machine harness remains disconnected from the switch.
Disconnect the machine harness connector(s) from the ECM.
At the machine harness connector for the ECM, measure the resistance from contact J1-24 (wire 973-BU), contact J1-20 (wire 974-BR), and contact J1-39 (wire 972-GN) of the machine harness to all the contacts that are used in the machine harness connectors for the ECM.Expected Result:Each resistance measurement is greater than 5000 ohms.Results:
YES - Each resistance measurement is greater than 5000 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 diagnostic code is not found, replace the ECM. See Testing And Adjusting, "Electronic Control Module (ECM) - Replace". Stop.
NO - One or more of the measurements were less than 5 ohms. There is a short in the machine harness.Repair: The short is between wire 973-BU and the circuit with the lowest resistance measurement, wire 974-BR and the circuit with the lowest resistance measurement, or the short is between wire 972-GN and the circuit with the lowest resistance measurement. Repair the machine harness or replace the machine harness. Stop.Test Step 3. CHECK THE OPERATION OF THE SWITCH (POWER POSITION)
Remove the jumper that was installed in the previous Test Step.
The machine harness remains disconnected from the switch.
Rotate the switch to the power position.
Connect one lead from a multimeter to contact