SHAFT 1N9155 - Caterpillar

Possible causes for an FMI 3 diagnostic code are:
The return circuit is open.
The signal circuit is open or the alarm is disconnected.
The signal circuit is shorted to the +battery.
The alarm has failed.
The ECM has failed. This condition is unlikely.Possible causes for an FMI 5 diagnostic code are:
The alarm has failed.
The signal circuit for the alarm is shorted to ground.
The ECM has failed. A failure of the ECM is unlikely.Possible causes for an FMI 6 diagnostic code are:
The energize circuit of the backup alarm is shorted to ground.
The backup alarm has failed.
The ECM has failed. This condition is unlikely.
Illustration 1 g03528278
Schematic of the Alarm
Note: The diagram above is a simplified schematic of the Transmission ECM and the Alarm connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision 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.
Table 2
Troubleshooting Test Steps Values Results
1. Identify The Active FMI Code Associated With The Suspect Circuit
Code present. FMI 3 diagnostic code, proceed to Test Step 2.
FMI 5 diagnostic code, proceed to Test Step 5.
FMI 6 diagnostic code, proceed to Test Step 7.
Begin Process For FMI 3 Troubleshooting HERE
2. Check The Alarm
A. Turn the key start switch and the disconnect switch to the OFF position.
B. Disconnect the alarm from the harness.
C. Use jumpers to connect the respective terminals of the alarm to +battery and ground.
D. Turn the key start switch and the disconnect switch to the ON position.
The alarm sounds. OK - The alarm sounds.
Proceed to Test Step 3.
NOT OK - The alarm does not sound.
Repair: Replace the alarm.
Proceed to Test Step 9.
3. Check For An Open In The Alarm Circuit
A. Turn the key start switch and disconnect switch to the OFF position.
B. The harness connector remains disconnected from the alarm.
C. Disconnect the J1 and J2 connectors from the ECM.
D. At the harness connector for the alarm, install a jumper wire.
E. At the harness connector for the ECM measure the resistance at the contacts for the alarm.
The resistance reading is less than 5 Ω. OK - The resistance is less than 5 Ω.
Proceed to Test Step 4.
NOT OK - The resistance is greater than 5K Ω.
Repair: Either the signal or the return circuit wire is open. Inspect all harness connection points for secure wire connections or corrosion. Repair or replace the harness, if necessary.
Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose connection or a corroded connection in the circuit. A resistance measurement greater than 5K Ω would indicate an open in the circuit.
Proceed to Test Step 9.
4. Check The Signal Circuit For