SHAFT AS-INPUT 7T5885 - Caterpillar

Machine ECM
The following is a list of diagnostic codes (SPN) associated with the Speed Sensors of the machine.
Table 1
Machine ECM (MID 39)
SPN-FMI Code Description System Response
6728-8 Vibration Sensor #1 : Abnormal frequency, pulse width, or period Turn Off Front Vibe
Fault Level - 2
6729-8 Vibration Sensor #2 : Abnormal frequency, pulse width, or period Turn Off Rear Vibe
Fault Level - 2 Possible causes for an FMI 8 diagnostic code are:
The sensor has failed.
The spacing of the sensor is incorrect.
The signal circuit of the speed sensor is open.
Intermittent connections or poor connections.
Mechanical devices are loose.
Incorrect software is loaded to the ECM.
The ECM has failed. A failure of the ECM is unlikely.
Illustration 1 g03828496
Speed Sensor connections
Note: The diagram above is a simplified schematic of the Machine ECM connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR6464 for the complete schematic.Diagnostic Trouble Code Procedure
Note: Prior to beginning this procedure, inspect the harness connectors that are involved in this circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure, and in good condition. If a problem with a connection is found, correct the problem and verify that the diagnostic code is active before performing a troubleshooting procedure. For sensors powered via the fuse panel, check the condition of the appropriate fuse before beginning the troubleshooting procedure.
Table 2
FMI 8 Troubleshooting
Troubleshooting Test Steps Values Results
1. Verify The Software Version
A. Check and record the latest software version for the machine electronic controls from SIS.
B. Verify that the latest version of software has been loaded to the ECM.
The software is current. OK - All of the software is current.
Proceed to Test Step 2.
NOT OK - There is a more recent software release that is available.
Repair: Flash all controls with the latest software release. Refer to Troubleshooting, "ECM Software - Install".
Proceed to Test Step 4.
2. Check The Signal Circuit For An Open
A. The key start switch and the disconnect switch remain in the OFF position.
B. Disconnect the machine harness connector from the sensor.
C. Disconnect the machine harness connectors from the ECM.
D. At the harness connector for the sensor, place a jumper wire between the signal contact and the return contact.
E. At machine harness connector for ECM, measure the resistance between the signal contact the return contact.
The resistance value is less than 5 Ω. OK - The resistance value is less than 5 Ω. The harness is correct.
Proceed to Test Step 3.
NOT OK - The resistance is greater than 5K Ω. There is an open circuit in the signal circuit or the return circuit.
Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose connection or corroded connection in the circuit. A resistance value that is greater than 5K Ω would indicate an open in the circuit.
Repair: Repair or replace the machine harness.
Proceed to Test Step 4.
3. Check The Signal Circuit For A Short
A. The