FITTING-UNION 4C3974 - Caterpillar

Table 6
Troubleshooting Test Steps Values Results
1. Identify The Active FMI Code Associated With The Sensor Circuit
Code present. FMI 2 diagnostic code, proceed to Test Step 2.
FMI 3 diagnostic code, proceed to Test Step 4.
FMI 4 diagnostic code, proceed to Test Step 9.
Begin Process For FMI 2 Troubleshooting HERE
2. Check The Circuit For A Short
A. Turn the key switch OFF.
B. Disconnect the switch from the machine harness.
C. Disconnect the J1 and J2 machine harness connections from the ECM.
C. At the machine harness connector for the ECM, measure the resistance between each of the signal contacts to every other contact used in the J1 and J2 machine harness connectors.
The resistance is greater than 5K ohms. OK - The resistance is correct.
Proceed to Test Step 3.
NOT OK - The resistance check is not correct.
Repair: There is a short in the signal circuits of the machine harness. Repair or replace the machine harness.
STOP
3. Check the Operation of the Switch.
A. The key switch remains OFF.
B. Reconnect all harness connectors.
C. Check the operation of the switch. Refer to the table for the suspected faulty switch at the beginning of this procedure for switch operation.
The switch operates correctly. OK - The switch is operating correctly.
Proceed to Test Step 12.
NOT OK - The switch is not operating correctly. The switch has failed.
Repair: Replace the switch.
STOP
Begin Process For FMI 3 Troubleshooting HERE
4. Check the Harness For an Open
A. Turn key start switch and disconnect switch OFF.
B. Disconnect the switch from the machine harness.
C. Disconnect the J1 and J2 machine harness connectors at the ECM.
D. At the machine harness connector for the switch, place a jumper between the two signal wires at the switch connector. Check for low resistance at the ECM connector
E. At the machine harness connect for the ECM, measure the resistance between the signal contact and frame ground.
The resistance is less than 5 ohms. OK - The circuit is correct.
Proceed to Test Step 5.
NOT OK - The resistance is greater than 5K ohms. The circuit is open.
Repair: Repair or replace the machine harness.
Note: A resistance that is greater than 5 ohms but less than 5K ohms indicates a loose connection