120M Series 2, 12M Series 2, 140M Series 2 and 160M Series 2 Motor Graders All Wheel Drive Electronic Control System Caterpillar

Illustration 1	g01377703
Schematic of the right front drive motor speed sensor

This diagnostic code is recorded when the all wheel drive ECM detects a number one right motor speed sensor signal that has an abnormal frequency. The FMI 02 diagnostic code is activated when the ECM detects an abnormal output frequency of the sensor.

The following conditions could cause this diagnostic code to be activated:

• The power wire (T800-OR) for the sensor is open.

• The return wire (J767-GY) for the sensor is open.

• The return wire (J767-GY) for the sensor is shorted to the + battery circuit.

• The signal wire (J718-OR) is open.

• The signal wire (J718-OR) is shorted to the + battery circuit.

• The signal wire (J718-OR) is shorted to ground.

• The sensor is faulty.

• The ECM is faulty. This is unlikely.

Test Step 1. CHECK THE RETURN CIRCUIT

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

2. Disconnect the machine harness from the sensor.

3. At the machine harness connector for the sensor, measure the resistance from contact 2 (wire J767-GY) of the machine harness to frame ground.

Expected Result:

The resistance is 5 ohms or less.

Results:

• OK - The resistance is 5 ohms or less. The return circuit is correct. Proceed to Test Step 2.

• NOT OK - The resistance is greater than 5000 ohms. The return circuit is open.

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

  STOP

Test Step 2. CHECK THE VOLTAGE AT THE SENSOR

1. The machine harness connector remains disconnected from the sensor.

2. Turn the key start switch to the ON position.

3. At the machine harness connector for the sensor, measure the voltage between contact 1 (wire T800-OR) and contact 2 (wire J767-GY).

Expected Result:

The voltage measures approximately 8 DCV.

Results:

• OK - The voltage measures approximately 8 DCV. Proceed to Test Step 3.

• NOT OK - The voltage does not measure approximately 8 DCV.

  Repair: Wire T800-OR is open. Repair the machine harness or replace the machine harness.

  STOP

Test Step 3. CHECK THE SIGNAL CIRCUIT FOR AN OPEN

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

2. The machine harness connector remains disconnected from the sensor.

3. Remove the machine harness connectors from the all wheel drive ECM.

4. At the machine harness connector for the sensor, place a jumper from contact 2 (wire J767-GY) to contact 3 (wire J718-OR).

5. At the machine harness connector for the ECM, measure the resistance from contact J1-3 and contact J1-45.

Expected Result:

The resistance is 5 ohms or less.

Results:

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

• NOT OK - The resistance is greater than 5000 ohms. The signal circuit is open.

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

  STOP

Test Step 4. CHECK THE SIGNAL CIRCUIT FOR A SHORT

1. The machine harness connector remains disconnected from the sensor and the ECM.

2. The key start switch remains in the OFF position.

3. Remove the jumper at the machine harness connector for the sensor.

4. At the machine harness connector for the ECM, measure the resistance between J1-3 (wire J718-OR) to all contacts that are used in the machine harness.

Expected Result:

Each resistance measurement is greater than 5000 ohms.

Results:

• OK - Each resistance measurement is greater than 5000 ohms. Proceed to Test Step 5.

• NOT OK - Each resistance measurement is not greater than 5000 ohms. There is a short between the signal circuit (wire J718-OR) and the circuit with the low resistance.

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

  STOP

Test Step 5. CHECK IF THE DIAGNOSTIC CODE REMAINS.

1. Perform the following:
   • Visually inspect the harness connectors.

   • Clean the contacts of the harness connectors.

2. Reconnect all harness connectors.

3. Turn the disconnect switch to the ON position.

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

5. Operate the machine in fourth gear of manual mode.

6. Check the status of the CID 2321 FMI 02.

Expected Result:

The CID 2321 FMI 02 is active.

Results:

• OK - The CID 2321 FMI 02 is active. The diagnostic code has not been corrected. The ECM may have failed. Proceed to Test Step 6.

• NOT OK - The CID 2321 FMI 02 is not active. The diagnostic code does not exist at this time.

  Repair: The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation.

  STOP

Test Step 6. CHECK THE SIGNAL FROM THE SENSOR

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

2. At the machine harness connector for the all wheel drive ECM, insert a 7X-1710 Multimeter Probe along the contact J1-3 (wire J718-OR).

3. Insert the other 7X-1710 Multimeter Probe along the contact J1-45 (wire J767-GY).

4. Set up a 146-4080 Digital Multimeter or similar meter in order to measure frequency.

5. Start the machine and operate the machine in a low gear with AWD in manual mode and the aggression dial at the center detent position.

6. Monitor the frequency of the sensor.

Expected Result:

The frequency is approximately 38 Hz for every km/h (61 Hz for every mph).

Results:

• OK - The frequency is correct.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM must be replaced, refer to the Testing and Adjusting, "Electronic Control Module (ECM) - Replace" Story in this manual for additional information.

  STOP

• NOT OK - The frequency is not correct.

  Repair: The speed sensor has failed. Replace the sensor.

  STOP