PISTON 7Y4621 - Caterpillar

Illustration 1 g06207822The preceding diagram is a simplified schematic of the RADAR Sensor power supply connections. The schematic is electrically correct, however, not all the possible harness connectors are shown. Refer to the latest revision of the electrical schematic to view the entire circuitry of the machine.Diagnostic Trouble Code Procedure
Table 2
Troubleshooting Test Steps Values Results
1. Identify The Active FMI Code Associated With The Sensor Supply Circuit Code present FMI 03 diagnostic code, proceed to Test Step 2.
FMI 04 diagnostic code, proceed to Test Step 5.
Begin Process For FMI 03 Troubleshooting HERE
2. Check The Sensor Supply Voltage At The Sensors
A. Turn the key start switch and the disconnect switch ON.
B. Disconnect the machine harness connector from the sensors.
C. At the machine harness connector for the sensors, measure the voltage between the voltage supply contact and the voltage return contact.
Voltage is 12.0 VDC 0.6 VDC. OK - The voltage is appropriate for the circuit as determined by the schematic. Verify that the diagnostic code is present.
If the code is still active, go to Test Step 4.
NOT OK - The reading is NOT the appropriate voltage as determined by the schematic. The voltage is greater than the expected voltage for the circuit based on the schematic. The sensor supply voltage is NOT correct.
Proceed to Test Step 3.
3. Check For A Short Circuit In The Machine Harness
A. Turn the key start switch and the disconnect switch OFF.
B. Disconnect the machine harness connectors from the ECM.
C. Disconnect the sensors from the machine harness.
D. Measure the resistance from the voltage supply wire to all other contacts in the harness.
The resistance is greater than 5K Ω. OK - Each resistance measurement is greater than 5K Ω. The ground circuit is correct.
Proceed to Test Step 4.
NOT OK - One or more of the resistance measurements is less than 5 Ω. There is a short circuit. The supply wire is shorted to whichever resistance measurement was low.
Repair: Repair or replace the machine harness. Confirm that the harness repair or replacement has corrected the problem. If the diagnostic code is present after harness repair or replacement, replacement of the ECM may be necessary.
Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. Review the diagnostic code list in Cat ET and compare the wire connection points on the schematic. Review the schematic for shared sensor connections associated with multiple sensor failures when searching for suspect connections. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.
4. Check The Voltage At The ECM
A. Turn the key start switch and the battery disconnect switch to the OFF position.
B. Connect the harness connectors to the ECM.
C. At the machine harness connector for the ECM, insert a 7X-1710 Multimeter Probe along the contact for the sensor power. Insert another probe along the return contact for the sensor power.
D. Turn the disconnect switch and key start switch to the ON