ROLLER GP-TRACK-SINGLE FLANGE 3550374 - Caterpillar

Illustration 1 g02260774
Schematic for the Cab AC Temperature sensor
This diagnostic code is associated with the Cab AC Temperature sensor. An FMI 04 means the Brake ECM has determined the voltage level of the sensor (wire C552-WH(White)) is below normal.Possible causes of the diagnostic code are:
The sensor signal output circuit is shorted to ground.
The sensor has failed.
The Brake ECM may have failed, but 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 connections in the circuit are clean, that all connections are secure and that all connections 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 Cab AC Temperature sensor from the machine harness.
Observe the status of the diagnostic code. Expected Result:The CID 0779 FMI 04 diagnostic code remains active.Results:
YES - The diagnostic code remains active. The sensor is correct. Proceed to Test Step 2.
NO - 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 Cab AC Temperature sensor.
Disconnect both the J1 and J2 machine harness connectors from the Brake ECM.
At the J1 harness connector for the Brake ECM, measure the resistance from signal contact J1-29 (wire C552-WH(White)) to all possible sources of ground in both the J1 and J2 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 machine harness is correct. Proceed to Test Step 3.
NO - One or more resistance measurements is not correct. There is a short in the machine harness. Repair: The short is between signal contact J1-29 (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 IF THE DIAGNOSTIC CODE REMAINS.
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 active. Results:
YES - The CID 0779 FMI 04 diagnostic code is