COVER AS 1318828 - Caterpillar

Illustration 1 g03326540
Schematic of the temperature sensor for the recirculation filter (cab temp)
The CID 0779 FMI 04 diagnostic code is associated with the temperature sensor for the recirculation filter. The FMI 04 means that the Implement ECM has determined that the voltage of the circuit for the sensor is below normal.The possible causes of this diagnostic code are listed below:
The signal circuit for the sensor is shorted to ground.
The sensor has failed.
The ECM has failed. This condition is unlikely. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean. Verify that all connections in the circuit are secure. Verify that all connections in the circuit are in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 0779 FMI 04 is active before performing this procedure. Note: Use a digital multimeter for the measurements in this procedure.System Response:A level 1 warning will be generated.Test Step 1. CHECK THE SENSOR
Turn the disconnect switch and the key start switch to the ON position.
Ensure that the diagnostic code is active.
Disconnect the sensor from the machine harness.
Observe the status of the diagnostic code. Expected Result:The CID 0779 FMI 04 diagnostic code remains active.Results:
OK - The diagnostic code remains active. The sensor is correct. Proceed to Test Step 2.
NOT OK - The diagnostic code changes from an FMI 04 to an FMI 03. The sensor has failed.Repair: Replace the sensor.STOPTest Step 2. CHECK THE WIRING HARNESS OF THE SENSOR FOR A SHORT TO GROUND
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness from the sensor.
Disconnect the machine harness connectors from the Implement ECM.
At the machine harness connector for the Implement ECM, measure the resistance from the signal contact J1-21 (wire C552-WH(White)) of the machine harness to all possible sources of ground. Measure the resistance to all contacts of the machine harness connectors for the Implement ECM. Expected Result:Each resistance measurement is greater than 5000 ohms.Results:
OK - Each resistance measurement is greater than 5000 ohms. The machine harness is correct. Proceed to Test Step 3.
NOT OK - One or more resistance measurements are not correct. There is a short in the machine harness.Repair: The short is between signal contact J1-21 (wire C552-WH(White)) and the circuit with the low resistance measurement. Repair the machine harness or replace the machine harness.STOPTest Step 3. CHECK THE STATUS OF THE DIAGNOSTIC CODE
Inspect the contacts of the harness connectors and clean the contacts.
Reconnect all harness connectors.
Turn the disconnect switch and the key start switch to the ON position.
Operate the machine.
Check the status of the CID 0779 FMI 04 diagnostic code. Expected Result:The CID 0779 FMI 04 diagnostic code is not active.Results:
OK