CAB G 0535526 - Caterpillar

Illustration 2 g03642897
Schematic of the Analog Active circuits
Note: The diagram above is a simplified schematic of the connections for the sensor signal (analog active) circuits. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic, UENR3102 for the complete schematic.Diagnostic Trouble Code Procedure
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.
Identify the active FMI code associated with the components.
Determine which code is present and use the list below to determine which procedure to follow.
FMI 3 diagnostic code, proceed to Table 3.
FMI 4 diagnostic code, proceed to Table 4.
Table 3
FMI 3 Troubleshooting
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 reading is correct for the sensor. OK - The voltage reading is correct for the sensor.
Proceed to Test Step 2.
NOT OK - The voltage is not correct for the circuit.
Proceed to Test Step 2.
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 ON.
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. Remove the jumper wire that was installed in the previous test step.
D. At the ECM harness connector, measure the resistance between the signal contact and all other +battery circuits used in the ECM harness connectors.
Each resistance