GEAR-PLANETARY 1210027 - Caterpillar

Illustration 1 g01208502
Schematic of the transmission gear selector switch (HMU).Thetransmission gear selector switch (HMU) has seven inputs to the power train electronic control module (ECM). During normal operation, one input is grounded and the other inputs are open. This diagnostic code of FMI 03 means that the ECM has determined that all contacts are open.Note: Ensure that the diagnostic code of CID 0702 FMI 03 is active before performing this procedure.Note: The following procedure can create other faults that can be detected by the power train ECM. Ignore these created faults and clear the created faults when the original diagnostic code is corrected.Test Step 1. CHECK FOR AN OPEN CIRCUIT
Turn the disconnect switch and the key start switch to the ON position.
Operate the machine.
Check the status of the CID 0702 FMI 03 while activating and deactivating each position of the directional switch. Note the results. Note: If the code does NOT remain active during operation of the switch, this could indicate a possible open (which corresponds to the switch position) in the harness.
Turn the disconnect switch and the key start switch to the OFF position.
Disconnect the machine harness connectors from the power train ECM.
At the machine harness connector for the power train ECM, check the continuity to ground of the open contacts and the grounded contact for each position of the transmission directional switch. Activate and deactivate each position of the transmission directional switch.Expected Result:The continuity checks do not agree with the ground and open combinations.Results:
YES - The continuity checks do NOT agree with the ground and open combinations. The harness or the transmission directional switch is faulty. Proceed to Test Step 2.
NO - The continuity checks agree with the ground and open combinations. Proceed to Test Step 3.Test Step 2. CHECK THE SWITCH
The disconnect switch and the key start switch remain in the OFF position.
The machine harness connectors remain disconnected from the power train ECM.
Disconnect the machine harness from the transmission directional switch.
Check the continuity to ground of the open contacts and the grounded contact for each position of the transmission directional switch. Activate and deactivate each position of the transmission directional switch. Expected Result:The continuity checks do not agree with the ground and open combinations.Results:
YES - The continuity checks do not agree with the ground and open combinations. The transmission directional switch is faulty.Repair: Repair the switch or replace the switch. Stop.
NO - The continuity checks agree with the ground and open combinations.Repair: Repair the machine harness or replace the machine harness. Stop.Test Step 3. CHECK FOR A SHORT TO THE +BATTERY.
At the machine harness connector for the power train ECM, check the continuity from each switch contact to all sources of battery voltage.Expected Result:Continuity exists between one of