CONTROLLER AS 3168386 - Caterpillar

Table 3
FMI 4 Troubleshooting
Troubleshooting Test Steps Values Results
1. Check The Sensors
A. Turn the key start switch and disconnect switch to the ON position.
B. Observe the status of the diagnostic code as each sensor is disconnected.
The FMI 4 diagnostic code is no longer active when one of the sensors on the supply circuit is disconnected. OK - The diagnostic code is not active when one of the sensors in the supply circuit is disconnected. The power supply circuit is correct.
Repair: Repeat this test step to determine the sensor that causes the problem. Replace the sensor causing the problem.
Proceed to Test Step 4.
NOT OK - The diagnostic code is still active. Disconnecting the sensors in the circuit did not affect the status of the diagnostic code.
Proceed to Test Step 2.
2. Check The Signal Circuit For A Short To Ground
A. Turn the key start switch and the disconnect switch to the OFF position.
B. Disconnect the harness connectors from the ECM.
C. Measure the resistance between the power supply contact and frame ground.
D. Measure the resistance between the power 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. The harness circuit is correct.
Proceed to Test Step 3.
NOT OK - The resistance is less than 5 Ω. The power supply circuit is shorted to ground. The short circuit exists between the power supply circuit and the circuit with the low-resistance measurement.
Repair: Repair or replace the machine harness.
Proceed to Test Step 4.
3. Check The Power Supply At The ECM
A. Turn the key start switch and disconnect switch to the OFF position.
B. At the harness connector for the ECM, use a 151-6320 Removal Tool to remove the supply wire and the sensor return wire from the connector. After the wires are removed, connect the wiring harness to the ECM.
C. Turn the disconnect switch and the key start switch to the ON position.
D. Use the multimeter probes in order 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 4.
NOT OK - The voltage measurement is less than the supply voltage. The measurement is not correct. The ECM has failed.
Proceed to Test Step 4.
4. Check If The Diagnostic Code Remains
A. Reconnect all harness connectors. Return machine to normal operating condition.
B. Turn the key start switch and the disconnect switch to the ON position.
C. Clear all diagnostic codes.
D. Operate the machine.
E. Stop the machine and engage the safety lock.
F. Check if the diagnostic code is active.
The diagnostic code is no longer present. OK - The diagnostic code does not exist at this time. The initial diagnostic code may have been caused by poor electrical connection or