ARM AS 4E2188 - Caterpillar

Table 1
Monitoring System (MID 30)
DTC Description System Response
263-3 Digital Sensor Power Supply (8V Or 12V) : Voltage Above Normal Sensors powered by the 8V supply will not function properly.
263-4 Digital Sensor Power Supply (8V Or 12V) : Voltage Below Normal Sensors powered by the 8V supply will not function properly. The diagnostic code is recorded when the interface module indicates that the voltage of the sensor supply circuit is too high, too low, or erratic.Possible causes of an FMI 03 Diagnostic code are:
The output of the sensor supply has shorted to the + battery circuit.
The monitor has failed. The monitor failing is unlikely.Possible causes of an FMI 04 Diagnostic code are:
The output of sensor supply has an open circuit.
A sensor has failed.
The monitor has failed. This situation is unlikely.Note: Before performing this procedure, verify that all circuit breakers and all fuses in the charging circuit and the monitor system supply circuit are closed. If a problem with a circuit breaker or a fuse is found, correct the problem, and check for codes before proceeding with the following steps. Note: Poor harness connections are often the cause of a problem in electrical circuits. Before performing this procedure, inspect all of the connectors involved in the circuit. Verify that all of the connections in the circuit are dry, clean, secure, and in good condition. Each pin and socket in the connectors should mate correctly when the connectors are fastened together. Check for exposed wires at the connectors for nicks or abrasion. If a problem is found with any of the connections: correct the problem and verify that diagnostic code is still active, before performing the following procedures. For more information, refer to Testing and Adjusting, "Electrical Connector - Inspect".Perform a wiggle test on the sensor circuit of the machine wiring harness, using Cat ET. The wiggle test can be used to detect open or shorted connections in the machine wiring harness. Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are fastened. For more information, refer to Testing and Adjusting, "Electrical Connector - Inspect".
Illustration 1 g02928678
Schematic of the 8 VDC Sensor Supply Voltage
Note: The diagrams above are a simplified schematic of the monitor connections. The diagrams are electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic, UENR3118 for the complete schematic.
Table 2
Troubleshooting Test Steps Values Results
1. Identify The Active FMI Code Associated With The Sensor Supply Circuit
Code present
FMI 3 diagnostic code, proceed to Test Step 3.
FMI 4 diagnostic code, proceed to Test Step 5.
2. Check The Voltage At The Monitor
A. Turn the key start switch and the battery disconnect switch to the OFF position.
B. At the machine harness connector for the monitor, insert a 7X-1710 Multimeter Probe along the contact for the sensor power. Insert another probe along the return contact for the sensor power.
C. Turn the disconnect switch to the ON position.
E. Observe the voltage measurement for