PISTON 1796928 - Caterpillar

Illustration 1 g02013414
Schematic of the "Continuous Flow Switch" circuitThis diagnostic code is associated with the "Loader Auxiliary Continuous Flow Switch" circuit. This switch has the following two inputs to the ECM:
Normally open wire (852-GN)
Normally closed wire (P993-OR)During normal operation, one switch input is open and the other input is grounded. If each input is shorted to the battery, the ECM will output the FMI 03 diagnostic code. This diagnostic code is detected when both switch inputs are shorted at the same time.The possible causes of this diagnostic code are listed below:
Short to the + battery terminal.
The circuit is open.
A failed switch
The ECM may have failed. This is unlikely.Note: 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 2735 FMI 03 is active before performing this procedure.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.Note: Use a calibrated digital multimeter for the measurements in this procedure.Test Step 1. CHECK THE CIRCUIT FOR THE SWITCH.
Turn the disconnect switch and the key start switch to the OFF position.
Disconnect the J1 and J2 machine harness connectors from the Machine ECM.
At the J1 machine harness connector, measure the resistance from contact J1-40 (wire 852-GN) to contact J2-37 (wire P993-OR) with the switch in the ENABLED position and the DISABLE position.Expected Result:The resistance should be the following:
Less than 5 ohms for the initial position of the switch
Greater than 5000 ohms for the opposite position of the switchResults:
YES - The resistance is correct for each measurement. Proceed to Test Step 3.
NO - The resistance measurement is greater than 5000 ohms for one or both measurements. The harness or the switch has failed. Proceed to Test Step 2.Test Step 2. CHECK FOR A SHORT.
Disconnect the switch from the harness.
At the J2 and J1 machine harness connectors, measure the resistance from contact J1-40 and contact J2-37 to all other J1 and J2 contacts.Expected Result:The resistance measurement should be greater than 5000 ohms for each measurement.Results:
OK - The resistance measurement is greater than 5000 ohms for each measurement. Proceed to Test Step 3.
NOT OK - The resistance measurement is not greater than 5000 ohms for one or more measurements.Repair: The short is in the circuit with the low resistance measurement. Repair the harness or replace the harness. Verify that the problem has been corrected.STOPTest Step 3. CHECK IF THE DIAGNOSTIC CODE REMAINS.
Inspect the contacts of the harness connectors. Clean the harness connectors.
Reconnect all the harness connectors.
Turn the disconnect switch and the key start switch to the ON position.
Operate the machine.
Check the status of the CID 2735 FMI 03 diagnostic