HARNESS AS-ENGINE 2217126 - Caterpillar

Illustration 1 g01126331
Schematic for Sensor Supply Voltage
This diagnostic code is associated with the power supply for the sensors. The FMI 04 means that the ECM has determined that the voltage of the sensor circuit is below normal.The possible causes of the diagnostic code are listed:
A sensor has failed.
The circuit is shorted to ground.
The ECM has failed. This is unlikely.Test Step 1. CHECK THE VOLTAGE AT THE ECM.
Turn the disconnect switch and the key start switch to the ON position.
Check the voltage at the harness connector for the ECM from contact J1-11 (wire R997-OR(Orange)) to contact J1-21 (L740-BR(Brown)). Use the 7X-1710 Cable probes to measure the voltage. Do NOT disconnect the machine harness from the ECM. Expected Result:The voltage is 5.0 0.5 DCV.Results:
OK - The voltage is 5.0 0.5 DCV. The sensor supply voltage is correct. Verify that the same diagnostic code is present. If the diagnostic code is still present the ECM may have failed.Repair: It is unlikely that the ECM has failed. Exit this procedure, and perform this procedure again. If the failure is not found, replace the ECM. See Troubleshooting, Testing and Adjusting, "Electronic Control Module (ECM) - Replace".STOP
NOT OK - The voltage is NOT 5.0 0.5 DCV. The voltage is less than 5.0 0.5 DCV. The sensor supply voltage is NOT correct. Proceed to Test Step 2.Test Step 2. CHECK FOR A SHORT TO GROUND
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness from the ECM.
At the harness connector for the ECM, measure the resistance between frame ground and contact J1-21 (L740-BR(Brown)). Expected Result:The resistance is greater than 5000 ohms.Results:
OK - The resistance is greater than 5000 ohms. Verify that the same diagnostic code is present. If the diagnostic code is still present the ECM may have failed.Repair: It is unlikely that the ECM has failed. Exit this procedure, and perform this procedure again. If the failure is not found, replace the ECM. See Troubleshooting, "Electronic Control Module (ECM) - Replace".STOP
NOT OK - Resistance is less than 5 ohms. The machine harness has failed or a sensor has failed. Proceed to Test Step 3.Test Step 3. DISCONNECT THE SENSORS.
The key start switch and the disconnect switch remain in the OFF position.
One at a time, disconnect any sensor that uses the power supply from the machine harness.
After disconnecting each sensor, check the resistance from frame ground to contact J1-11 at the harness connector for the ECM. Expected Result:After disconnecting a particular sensor, the resistance changes and the resistance is greater than 5000 ohms.Results:
YES - After disconnecting a particular sensor, the resistance changes and the resistance is greater than 5000 ohms. The sensor that was just disconnected has failed.Repair: Replace the sensor.STOP
NO - After disconnecting all of the sensors, the resistance is less than 5 ohms. The machine harness is shorted to ground.Repair: Repair the machine harness or replace the machine harness. STOP