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| Illustration 1 | g01458196 |
Schematic of the Temperature Sensor (Rear Axle Oil) | |
This diagnostic code is associated with the temperature sensor (rear axle oil). The FMI 08 means that the ECM has determined that the signal frequency or the signal pulse width is not within the expected range.
The sensor is a PWM sensor that operates at a frequency of approximately 500 hertz. The sensor has an operating duty cycle of 10% to 90%.
| TEMPERATURE | % DUTY CYCLE |
| -40°C (-40°F) | 10.01% |
| 120°C (248°F) | 89.26% |
The possible causes of this diagnostic code are listed below:
- The sensor has failed.
- Intermittent connections or poor connections
- Mechanical devices are loose.
- The ECM has failed. This 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 0428 FMI 08 is active before performing this procedure.
Note: Use a digital multimeter for the measurements in this procedure.
Test Step 1. CHECK FOR POWER AT THE SENSOR.
- Do not disconnect the harness connector from the sensor.
- At the back of the harness connector for the sensor, insert a multimeter probe along contact 1 (wire K983-BU) for the voltage supply.
- Turn the key start switch and the disconnect switch to the ON position.
- Measure the voltage from contact 1 (wire K983-BU) to contact 2 (wire J842-BK).
Expected Result:
The voltage is 8 ± 0.5 DCV.
Results:
- OK - The voltage is 8 ± 0.5 DCV. Proceed to Test Step 3.
- NOT OK - The voltage is not 8 ± 0.5 DCV. The circuit is open.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 2. CHECK THE SIGNAL CIRCUIT OF THE SENSOR.
- Turn the key start switch and the disconnect switch to the OFF position.
- At the back of the harness connector for the sensor, remove the multimeter probe from contact 1 and insert the probe along the signal wire (contact 3).
- At the back of the harness connector for the sensor, insert the multimeter probe along the ground wire (contact 2).
- Turn the disconnect switch and the key start switch to the ON position.
- Monitor the signal of the sensor with a digital multimeter.
- Without disconnecting the sensor or the hardware that is associated with the sensor from the machine, take the sensor through the full operating range of the sensor.
Expected Result:
The sensor's signal responds in the manner that is described at the beginning of this procedure.
Results:
- OK - The sensor's signal responds correctly. The sensor is operating correctly. Proceed to Test Step 3.
- NOT OK - The sensor's signal does not respond correctly. The sensor is NOT operating correctly.
Repair: Replace the sensor.
STOP
Test Step 3. CHECK THE SIGNAL CIRCUIT AT THE ECM.
- Turn the key start switch and the disconnect switch to the OFF position.
- Insert the multimeter probes into the back of the ECM connector along J2-19 (wire J842-BK) and J1-37 (wire 446-PU).
- Turn the disconnect switch and the key start switch to the ON position.
- Monitor the signal of the sensor with a digital multimeter.
- Without disconnecting the sensor or the hardware that is associated with the sensor from the machine, take the sensor through the full operating range of the sensor.
Expected Result:
The sensor's signal responds in the manner that is described at the beginning of this procedure.
Results:
- OK - The sensor's signal responds correctly. The sensor is operating correctly. Proceed to Test Step 4.
- NOT OK - The sensor's signal does not respond correctly. The harness has failed.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 4. CHECK THE SIGNAL CIRCUIT FOR A SHORT IN THE HARNESS.
- The key start switch and the disconnect switch remain in the OFF position.
- Disconnect the machine harness connectors from the sensor and the ECM.
- Measure the resistance between contact J1-37 (wire 446-PU) and all contacts that are used in the machine harness connectors for the ECM.
Expected Result:
The resistance is greater than 5000 ohms.
Results:
- OK - The resistance is greater than 5000 ohms. The circuit is correct. Proceed to Test Step 5.
- 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 5. CHECK IF THE DIAGNOSTIC CODE REMAINS
- Inspect the harness connectors. Clean the contacts of the harness connectors and check the wires for damage to the insulation that is caused by excessive heat, battery acid, or chafing.
- Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit.
- Reconnect all harness connectors. Make sure that the connectors are fully seated. Make sure that the clips for each connector are completely fastened.
- Turn the disconnect switch and the key start switch to the ON position.
- Operate the machine.
- Check the status of the CID 0428 FMI 08.
Expected Result:
The CID 0428 FMI 08 is not active.
Results:
- OK - The CID 0428 FMI 08 is not active. The diagnostic code does not exist at this time. The initial diagnostic code was probably caused by a poor connection or a short at one of the connectors that was disconnected and reconnected. Resume normal operation.STOP
- NOT OK - The CID 0428 FMI 08 is active. The diagnostic code has not been corrected.
Repair: Check the circuit again. The Caterpillar Electronic Technician (ET) (service tool) may be used in order to perform a "Wiggle Test" on the machine wiring harness. The "Wiggle Test" can detect intermittent shorts or intermittent opens in the machine wiring harness.It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the failure is not found, replace the ECM. See the Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP