CT660 CX31 and CX31 HT On Highway Truck Power Train Electronic Control System Caterpillar

Illustration 1	g01238171
Connections of the transmission oil temperature sensor

This diagnostic code is associated with the transmission oil temperature sensor. The FMI 0 means that the ECM has determined that the signal of the sensor is above the normal range.

The output frequency of the position sensor is approximately 500 Hz. The value of the sensor duty cycle is approximately 3.5% when the pedal is released. The duty cycle of the signal increases as the pedal is moved from the released position to the pressed position. The value of the sensor duty cycle is approximately 96.5% in the pressed position.

The possible causes of this diagnostic code are listed below:

• The sensor has failed.

• The signal circuit of the sensor is shorted to the + battery circuit.

• The sensor needs calibrated.

• The ECU has failed. The ECU failing is unlikely.

Note: The following test procedure may create other diagnostic codes. Ignore these diagnostic codes and clear these diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of SPN 177 FMI 0 is active before performing this procedure.

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

System Response:

A warning will be displayed on the Caterpillar Electronic Technician (Cat ET). The transmission will be placed in the neutral gear until the diagnostic code is cleared.

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 8.

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 the voltage supply wire (contact 1).

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

4. Measure the voltage from contact 1 to frame ground.

Expected Result:

The voltage is 12 DCV.

Results:

• OK - The voltage is 12 DCV. Proceed to Test Step 3.

• NOT OK - The voltage is not 12 DCV. The circuit is open.

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

  STOP

Test Step 3. CHECK FOR PROPER GROUND AT THE SENSOR.

1. The machine harness remains connected to the sensor.

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

3. Remove the multimeter probe from the voltage supply wire (contact 1).

4. At the back of the harness connector for the sensor, insert a multimeter probe along the ground wire (contact 2).

5. Measure the resistance from contact 2 to frame ground.

Expected Result:

The resistance is less than 5 ohms.

Results:

• OK - The resistance is less than 5 ohms. The ground circuit is correct. Proceed to Test Step 4.

• NOT OK - The resistance is greater than 5 ohms. The ground circuit in the machine harness has failed.

  Repair: Replace the machine harness or repair the machine harness.

  STOP

Test Step 4. 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 the ground wire (contact 2).

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

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 of the sensor.

   Note: On some machines, it may be necessary to start the engine in order to take the sensor through the full operating range of the sensor.

Expected Result:

The sensor signal responds in the manner that is described at the beginning of this procedure. The SPN 703 FMI 0 is not active at the maximum range of the sensor.

Results:

• OK - The sensor signal responds correctly. The sensor is operating correctly. Proceed to Test Step 5.

• NOT OK - The sensor signal does not respond correctly. The sensor is NOT operating correctly.

  Repair: Replace the sensor.

  STOP

Test Step 5. 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 J1-3 and J1-9.

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 of the sensor.

   Note: On some machines, it may be necessary to start the engine in order to take the sensor through the full operating range of the sensor.

Expected Result:

The sensor signal responds in the manner that is described at the beginning of this procedure. The SPN 703 FMI 0 is not active at the maximum range of the sensor.

Results:

• OK - The sensor signal responds correctly. The sensor is operating correctly. Proceed to Test Step 6.

• NOT OK - The sensor signal does not respond correctly. The harness has failed.

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

  STOP

Test Step 6. 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 J1-3 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 7.

• 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 7. CHECK IF THE DIAGNOSTIC CODE REMAINS

1. Inspect the harness connectors and clean the contacts of the machine harness connectors.

2. Reconnect all harness connectors.

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

4. Operate the machine and take the sensor through the operating range of the sensor.

5. Check the status of the diagnostic code.

Expected Result:

The diagnostic code is not active at the maximum range of the sensor.

Results:

• OK - The diagnostic code is not active at the maximum range of the sensor. 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 diagnostic code is active at the maximum range of the sensor. The diagnostic code has not been corrected. The ECM may have failed.

  Repair: It is unlikely that the ECM has failed. Exit this procedure. Perform the adjustment procedure for the sensor, if necessary. Then perform the calibration procedure for the sensor. Perform this procedure again. Prior to replacing an ECM, always contact your dealership for possible consultation with Caterpillar. If the ECM requires replacement, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP

Test Step 8. CHECK THE ADJUSTMENT AND/OR THE CALIBRATION OF THE SENSOR.

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

2. Perform the adjustment procedure for the position sensor, if necessary. Then perform the calibration of the position sensor. Refer to the Testing and Adjusting section of the manual for additional information on these procedures.

3. Without disconnecting the sensor or the hardware that is associated with the sensor, move the sensor through the entire range of motion.

   Note: On some machines, it may be necessary to start the engine in order to move the sensor through the entire range of motion.

4. Check the status of the diagnostic code.

Expected Result:

The diagnostic code is not active.

Results:

• OK - The diagnostic is not active. The adjustment and/or the calibration has corrected the failure. Resume normal operation.

  STOP

• NOT OK - The diagnostic code is still active.

  Repair: Exit this procedure. Perform this procedure again.

  STOP