HOUSING 8N2699 - Caterpillar

Possible Causes for an FMI 3 Diagnostic code are:
The power supply circuit for the sensor is open.
The return circuit is open.
The signal circuit is open or the sensor is disconnected.
The signal circuit is shorted to the sensor power supply.
The sensor has failed.
The Machine ECM has failed. This situation is unlikely.Possible Causes for an FMI 4 Diagnostic code are:
The signal circuit for the sensor is shorted to ground.
The sensor has failed.
The Machine ECM has failed. A failure of the Machine ECM is unlikely.
Illustration 1 g06325996
Sensor Signal (Analog, Active) schematic
Note: The diagram above is a simplified schematic of the Machine ECM connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, M0094859 for 320D3 and M0094901 for 323D3 excavator electrical systems.Diagnostic Trouble Code Procedure
Note: Prior to beginning 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, secure and 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.
Identify the active FMI code associated with the faulty component.
Determine which code is present and use the list below to determine the correct procedure to follow.
FMI 3 diagnostic code, proceed to Table 2.
FMI 4 diagnostic code, proceed to Table 3.
Table 2
Begin Process For FMI 3 Troubleshooting HERE
Troubleshooting Test Steps Values Results
1. Check The Voltage At The Sensor
A. Turn key start switch and disconnect switch ON.
B. Refer to the schematic to determine the voltage source for the sensor.
C. At the machine harness connector for the sensor, insert 7X-1710 multimeter probes along the sensor supply and sensor return.
D. At the sensor harness connector, measure voltage between the sensor supply and sensor return.
Voltage is 5.0 VDC 0.3. OK - Voltage is 5.0 VDC 0.3.
Proceed to Test Step 2.
NOT OK- Voltage is NOT 5.0 VDC 0.3.
Repair - Check the machine harness for damage. Repair or replace the machine harness.
STOP
2. Check The Harness 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. At the sensor harness connector, install a jumper wire between the sensor return contact and signal contact.
D. Turn the key switch and disconnect switch to the ON position.
E. Observe the status of the diagnostic code.
The diagnostic code changes from an FMI 3 to an FMI 4. OK – The diagnostic code changes from an FMI 3 to an FMI 4. The sensor has failed.
Repair: Replace the sensor.
Proceed to Test Step 4.
NOT OK – The diagnostic code does not change from an FMI 3 to an FMI 4.
Proceed to Test Step 3.
3. Check Signal Circuit For A Short To +Battery
A. Turn the key start switch and the disconnect switch to the OFF position.
B. Disconnect the ECM harness connectors. The sensor harness connector remains disconnected.
C.