WASHER 4797828 - Caterpillar

Illustration 1 g00939825
This diagnostic code is associated with the left material height dial (potentiometer) for the screed. The FMI 04 means that the ECM has determined that the voltage of the circuit for the sensor is below normal. The output frequency of the sensor is approximately 500 Hz. The duty cycle of the signal varies as the position sensor moves. The duty cycle varies from 2% to 98%. The operation of the potentiometer is a linear resistance that will vary from approximately 0 ohms to 1000 ohms.The possible causes of this diagnostic code are listed below:
The signal circuit for the sensor is shorted to ground.
The sensor has failed.
The ECM has failed. ECM failure is unlikely. Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 0978 FMI 04 is active before performing this procedure. Note: Use the 146-4080 Digital Multimeter for the measurements in this procedure.System Response:The machine ECM will maintain the current value until a neutral reset occurs. The machine ECM will default to 50 percent after a neutral reset has occurred. The fault lamp for the material system, the tamp system, and the auxiliary system is activated.Test Step 1. CHECK THE SENSOR
Turn the disconnect switch and the key start switch to the ON position.
Ensure that the diagnostic code is active.
Observe the status of the diagnostic code. Disconnect the sensor from the machine harness.Expected Result:The CID 0978 FMI 04 remains active. The FMI has not changed and the "04" is still active.Results:
OK - The diagnostic code remains active. The sensor is correct. Proceed to Test Step 2.
NOT OK - The diagnostic code is no longer active. The sensor has failed.Repair: Replace the sensor.STOPTest Step 2. CHECK THE WIRING HARNESS OF THE SENSOR FOR A SHORT TO GROUND.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness from the sensor.
Disconnect the machine harness connectors from the ECM.
At the machine harness connector for the ECM, measure the resistance from the signal contact J1-4 (wire M906-BU) of the machine harness to all possible sources of ground. Measure the resistance to all contacts of the machine harness connectors for the ECM.Expected Result:Each resistance measurement is greater than 5000 ohms.Results:
OK - Each resistance measurement is greater than 5000 ohms. The machine harness is correct. Proceed to Test Step 4.
NOT OK - One or more resistance measurements are not correct. There is a short in the machine harness. Repair: The short is between signal contact J1-4 (wire M906-BU) and the circuit with the low resistance measurement. Repair the machine harness or replace the machine harness.STOPTest Step 3. CHECK THE POTENTIOMETER
Access the potentiometer that is located in the left control box on the screed.
Attach a 6V-7070 Digital Multimeter with 7X-1710 Multimeter Probes to the receptacle of the potentiometer without disconnecting the connectors. Connect the ground lead to pin "B" and connect the signal