777G Off-Highway Truck Chassis Electronic Control System Caterpillar

Illustration 1	g02667117
Schematic of the "Hoist Lever Position" sensor

This diagnostic code is associated with the "Hoist Lever Position" sensor. The FMI 04 diagnostic code means that the ECM has determined that the voltage of the circuit for the position sensor is below normal.

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 Chassis ECM has failed. A failure of the ECM 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 0773 FMI 04 is active before performing this procedure.

Note: Use a digital multimeter for the measurements in this procedure.

Test Step 1. INSPECT THE SENSOR.

1. Perform a visual inspection of the sensor, the wiring for the sensor and the hardware that is associated with the sensor.

Expected Result:

There is no apparent damage to the sensor, the wiring for the sensor or the hardware that is associated with the sensor.

Results:

• OK - There is no apparent damage to the sensor, the wiring for the sensor or the hardware that is associated with the sensor. Proceed to Test Step 2.

• NOT OK - There is apparent damage to the sensor, the wiring for the sensor or the hardware that is associated with the sensor.

  Repair: Replace the damaged part.

  Proceed to Test Step 2.

Test Step 2. CHECK FOR POWER AT THE SENSOR.

1. Do not disconnect the harness connector from the sensor.

2. At the back of the harness connector for the sensor, insert a multimeter probe along contact 1 (wire 104-YL) for the voltage supply.

3. Turn the key start switch and the disconnect switch to the ON position.

4. Measure the voltage from contact 1 (wire 104-YL) to contact 2 (wire J764-BR).

Expected Result:

The voltage is between 9 VDC and 32 VDC.

Results:

• OK - The voltage is between 9 VDC and 32 VDC. Proceed to Test Step 3.

• NOT OK - The voltage is not between 9 VDC and 32 VDC. The circuit is open.

  Repair: Repair the machine harness or replace the machine harness.

  STOP

Test Step 3. CHECK THE SIGNAL OF THE SENSOR.

1. Turn the key start switch and the disconnect switch to the OFF position.

2. The multimeter probe remains along contact 2 (wire J764-BR).

3. At the back of the harness connector for the sensor, insert the other multimeter probe along contact 3 (wire M996-PK).

4. Turn the disconnect switch and the key start switch to the ON position.

5. Monitor the signal of the sensor with the digital multimeter.

6. Without disconnecting the sensor (or the hardware that is associated with the sensor) from the machine, take the sensor through the full operating range.

Expected Result:

The signal from the sensor responds in the manner that is described at the beginning of this procedure. The CID 0773 FMI 04 diagnostic code is not active at the maximum range of the sensor.

Results:

• OK - The signal from the sensor is correct. The sensor is operating correctly. Proceed to Test Step 4.

• NOT OK - The signal from the sensor is not correct. The sensor is NOT operating correctly.

  Repair: Replace the sensor.

  STOP

Test Step 4. CHECK THE SIGNAL AT THE ECM.

1. Turn the key start switch and the disconnect switch to the OFF position.

2. Insert the multimeter probes into the back of the ECM connector along J2-15 (wire M996-PK) and J2-63 (wire J764-BR).

3. Turn the disconnect switch and the key start switch to the ON position.

4. Monitor the signal of the sensor with the digital multimeter.

5. Without disconnecting the sensor or the hardware that is associated with the sensor from the machine, take the sensor through the full operating range.

Expected Result:

The signal of the sensor responds in the manner that is described at the beginning of this procedure. The CID 0773 FMI 04 diagnostic code is not active at the maximum range of the sensor.

Results:

• OK - The signal of the sensor is correct. The sensor is operating correctly. Proceed to Test Step 5.

• NOT OK - The signal of the sensor is not correct. The harness has failed.

  Repair: Repair the machine harness or replace the machine harness.

  STOP

Test Step 5. CHECK THE SIGNAL CIRCUIT FOR A SHORT IN THE HARNESS.

1. The key start switch and the disconnect switch remain in the OFF position.

2. Disconnect the machine harness connectors from the sensor and the ECM.

3. Measure the resistance between contact J2-15 (wire M996-PK) and all contacts that are used in the machine harness connectors for the ECM.

Expected Result:

Each resistance measurement is greater than 5000 ohms.

Results:

• OK - Each of the resistance measurements are greater than 5000 ohms. The circuit is correct. Proceed to Test Step 6.

• NOT OK - The resistance is less than 5 ohms. The signal circuit is shorted to another circuit in the harness.

  Repair: Repair the machine harness or replace the machine harness.

  STOP

Test Step 6. CHECK IF THE DIAGNOSTIC CODE IS STILL ACTIVE.

1. Inspect the harness connectors. Clean the contacts of the harness connectors. Check the wires for damage to the insulation that is caused by excessive heat, battery acid, or chafing.

2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit.

3. Reconnect all harness connectors in order to make sure that the connectors are fully seated. Make sure that the clips for each connector are fastened securely.

4. Turn the disconnect switch and the key start switch to the ON position.

5. Operate the machine.

6. Determine if the CID 0773 FMI 04 diagnostic code is active.

Expected Result:

The CID 0773 FMI 04 diagnostic code is active.

Results:

• YES - The CID 0773 FMI 04 diagnostic code is active. The problem has not been corrected.

  Repair: Check the circuit again. Use the Cat ET service tool in order to perform a "Wiggle Test" on the machine wiring harness. The "Wiggle Test" can detect momentary short circuits and intermittent open circuits in the wiring harness of the machine. A failure of the ECM is unlikely. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. Prior to replacing an ECM, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP

• NO - The CID 0773 FMI 04 diagnostic code is not active. The problem does not exist at this time. The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors. Resume normal machine operation.STOP