GRID AS 1684591 - Caterpillar

The preceding diagram is a simplified schematic of the connections for the sensor supply circuits. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of the applicable electrical schematic to view the entire circuitry of the machine.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. Check the wiring for pinch points or abrasions. Look for and repair areas that indicate wires are exposed. If a problem with a connection is found, correct the problem and verify that this 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 2.
FMI 4 diagnostic code, proceed to Table 3.
Table 2
FMI 3 Troubleshooting
Troubleshooting Test Steps Values Results
1. Check The Voltage At The Sensors
A. Turn key start switch and disconnect switch ON.
B. Disconnect the machine harness connector for the sensors.
C. At the machine harness connector for the sensors, measure the voltage between the sensor supply contact and the sensor return contact.
Voltage reading is correct for the sensors. OK - The voltage reading is correct for the sensors.
Proceed to Test Step 4.
NOT OK - The voltage is greater than the supply for the circuit.
Proceed to Test Step 2.
2. Check The Power Supply At The ECM
A. Turn the key start switch and disconnect switch to the OFF position.
B. At the J1 harness connector for the ECM, use a 151-6320 Removal Tool to remove the supply wire and the sensor return wire. The harness connector remains connected to the ECM.
C. Turn the disconnect switch and the key start switch to the ON position.
D. Use the multimeter probes to make contact on the connector pins. Measure the voltage at the ECM pins between the sensor supply contact and sensor return contact .
Voltage reading is correct for the supply. OK - The voltage is correct. The ECM power supply is correct. Install the wires and sockets that were removed from the ECM connector back into the original locations.
Proceed to Test Step 3.
NOT OK - The voltage measurement is greater than the supply voltage. The measurement is not correct. The ECM may have failed.
Proceed to Test Step 4.
3. Check For A Short In the Harness
A. The sensors remain disconnected from the machine harness.
B. The key start switch and disconnect switch remainOFF.
C. Disconnect the machine harness connectors from the ECM.
D. At the ECM harness connector, measure the resistance between the supply contact and all the other contacts that are used for the ECM.
Each resistance is greater than 5K Ω. OK - Each resistance is greater than 5K Ω.
Proceed to Test Step 4.
NOT OK - One or more readings less than 5 Ω. There is