AP600D, AP655D, BG600D and BG655D Asphalt Pavers Caterpillar

Illustration 1	g01521798
Schematic for Left and Right Drive Motor Speed Sensors

This diagnostic code is associated with the Left Drive Speed Sensor. The FMI 08 means that the ECM has determined that the signal frequency or the signal pulse width is not within the expected range.

There will be two monitored sensor signals for each motor. One of the signals is primary and one signal is secondary. A diagnostic code is generated if the primary signal and the secondary signal differ by more than 35 rpm for a time greater than the debounce time.

Note: The "Machine ECM" is located inside the center console that is mounted to the access door.

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 0154 FMI 08 is active before performing this procedure.

Note: Use the 146-4080 Digital Multimeter for the measurements in this procedure.

System Response:

When this diagnostic code is active, the following occurs:

• The machine operates in open loop mode.

• The speed limit is applied in travel mode.

• The operator station fault lamp is active.

Test Step 1. CHECK THE RETURN CIRCUIT

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

2. Disconnect the machine harness connector from the sensor.

3. At the machine harness connector for the sensor, measure the resistance between return circuit J1-45 (C234-BK) and the frame ground.

Expected Result:

The resistance should measure 5 ohms or less.

Results:

• OK - The return circuit is correct. Proceed to test step 2.

• NOT OK - The return circuit (C234-BK) in the machine harness is open.

  Repair: Repair the harness or replace the harness.

  STOP

Test Step 2. CHECK THE POWER SUPPLY CIRCUIT AT THE SENSOR

1. The machine harness remains disconnected from the sensor.

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

3. At the machine harness for the sensor, measure the voltage. Measure the voltage from contact 1 (wire A105-OR) and contact 3 (wire C234-BK).

Expected Result:

The voltage that is measured is between 8 ± 0.5 DCV.

Results:

• OK - The power supply circuit is correct. Proceed to test step 3.

• NOT OK - The power supply circuit is open between the sensor and the ECM.

  Repair: Repair the harness or replace the harness.

  STOP

Test Step 3. CHECK THE ECM AND THE HARNESS.

1. The key start switch remains ON.

2. The machine harness remains disconnected from the sensor.

3. At the machine harness for the sensor, measure the voltage for the signal circuit 1. Measure the voltage from contact 2 (G808-BU) and contact 3 (C234-BK).

4. At the machine harness for the sensor, measure the voltage for the signal circuit 2. Measure the voltage from contact 4 (G809-GN) and contact 3 (C234-BK).

Expected Result:

The voltage that is measured is 5 ± 0.5 DCV for both measurements.

Results:

• OK - The signal circuits are correct. Proceed to test step 6.

• NOT OK - The machine harness or the ECM has failed. Proceed to test step 4.

Test Step 4. CHECK FOR A SHORT IN THE HARNESS.

1. The machine harness remains disconnected from the sensor.

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

3. Disconnect the machine harness connectors from the ECM.

4. Measure the resistance from the contact J2-26 (wire G808-BU) and contact J2-27 (wire G809-GN) of the machine harness to all contacts that are used in the machine harness connectors for the ECM.

Expected Result:

The resistance should be greater than 5000 ohms for each measurement.

Results:

• OK - The resistance is greater than 5000 ohms. The machine harness is correct. Proceed to test step 5.

• NOT OK - The resistance is NOT correct. There is a short in the machine harness. The short is between wire G808-BU and the circuit with the low resistance measurement or the short is between wire G809-GN and the circuit with the low resistance measurement.

  Repair: Repair the harness or replace the harness.

  STOP

Test Step 5. CHECK THE SIGNAL CIRCUITS FOR A SHORT TO GROUND.

1. The machine harness remains disconnected from the sensor.

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

3. The machine harness connectors remain disconnected from the ECM.

4. Measure the resistance from the sensor contacts J2-26 (wire G808-BU) and J2-27 (wire G809-GN) to all possible sources of ground.

Expected Result:

The resistance that is measured is greater than 5000 ohms for each measurement.

Results:

• OK - The resistance that is measured is greater than 5000 ohms for each measurement. Proceed to test step 6.

• NOT OK - There is a short in the machine harness.

  Repair: The short is between the wire for the sensor signal and the circuit with the low resistance measurement. Repair the machine harness or replace the machine harness.

  STOP

Test Step 6. INSPECT THE SENSOR.

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

2. The sensor remains disconnected from the machine harness.

3. Remove the speed sensor. Inspect the speed sensor for damage or the presence of a foreign material on the tip. Clean the tip. If the sensor is damaged, replace the sensor.

4. Install the speed sensor.

Expected Result:

The sensor is not damaged. The sensor is free of foreign material.

Results:

• OK - The sensor is not damaged. The sensor is free of foreign material. Proceed to test step 7.

• NOT OK - The sensor is damaged or the presence of a foreign material exists.

  Repair: Repair the sensor or replace the sensor.

  STOP

Test Step 7. CHECK IF THE DIAGNOSTIC CODE REMAINS.

1. Inspect the contacts of the harness connector. Clean the contacts of the harness connectors.

2. Reconnect all harness connectors.

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

4. Clear all inactive diagnostic codes.

5. Operate the machine.

6. Stop the machine and place the parking brake switch in the ON position.

7. Check if the diagnostic code for the sensor is active.

Expected Result:

The diagnostic code is NO longer active.

Results:

• OK - The diagnostic code is NO longer active. The diagnostic code 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 that was disconnected and reconnected. Resume normal machine operation.STOP

• NOT OK - The diagnostic code has not been corrected. The ECM may have failed.

  Repair: Prior to replacing an ECM, always contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP