854K Wheel Dozer Electrohydraulic System Caterpillar

Illustration 1	g02700318
Schematic of the Tilt Pump Pressure Sensor.

This diagnostic code is recorded when the ECM reads the input signal from the Tilt Hydraulic Pump Sensor and determines 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 500Hz ± 100Hz. The sensor sends a PWM input signal to the ECM. The duty cycle of the signal will vary from 2% to 98%.

If the PWM frequency is outside the 500Hz ± 100HZ operating range or the pulse width of the sensor input circuit is less than 2% or greater than 98%, an FMI 08 diagnostic code will be activated.

The signal may have one of the following characteristics:

• Abnormal frequency

• Abnormal pulse width

• Abnormal period

The possible causes of this condition are listed below:

• Intermittent connections or poor connections in the wire harness.

• The sensor has failed.

• The ECM has failed. This condition is unlikely.

Note: This diagnostic code is caused by an intermittent condition. The diagnostic code is active and the diagnostic code is inactive over time.

Note: Ensure that there are no active CID 262 diagnostic codes for the 8 VDC sensor power supply before performing this procedure. Ensure that CID 0767 FMI 08 diagnostic code is active. This test procedure may cause other diagnostic codes. Clear these diagnostic codes when the original diagnostic code has been corrected.

Test Step 1. CHECK THE DUTY CYCLE AND THE SIGNAL FREQUENCY AT THE SENSOR

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

2. At the machine harness connector for the sensor, use a 151-6320 Removal Tool to remove the signal wire M923-PU(Purple)and the socket at contact 3 from the harness connector. The connector for the machine harness remains connected to the sensor.

3. At the back of the connector of the sensor , insert 7X-1710 Multimeter Probes along the ground contact 2 and the signal contact at 3.

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

5. Measure the frequency of the signal from the sensor.

6. Observe the measurement and wiggle the connector of the sensor. Gently pull on the wires and wiggle the wires.

7. Measure the duty cycle of the sensor at the connector pins between the contacts 2 and 3.

Expected Result:

The frequency of the sensor signal is 500 ± 100 Hz. The duty cycle of the signal is correct according to the description at the beginning of this procedure. The frequency and the duty cycle are stable during the manipulation of the harness connector and the wiring.

Results:

• OK - The signal frequency and the duty cycle of the sensor is correct. The sensor is not the cause of the problem. Reconnect the wire and the socket into the original locations in the ECM connector. Verify that all wires of the sensor are secure in the connector. Proceed to Test Step 2.

• NOT OK - The signal frequency or the duty cycle of the sensor is not correct according to the description at the beginning of this procedure. The sensor has failed.

  Repair: Perform this test step again in order to verify that the sensor signal is not correct.

  The operation of the position sensor is not correct. Replace the sensor. After replacement, verify that the operation is correct before operating the machine.

  STOP

Test Step 2. CHECK FOR AN OPEN IN THE SENSOR CIRCUIT

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

2. Disconnect the machine harness connector from the sensor. At machine harness connector, place a jumper wire between the ground contact 2 (wire X998-BR(Brown)) and the signal contact 3 (wire M923-PU(Purple)).

3. Disconnect machine harness connectors J1 and J2 from the Implement ECM.

4. At the harness connectors for the ECM, measure the resistance between return contact J1-45 (wire X998-BR(Brown)) and signal contact J2-49 (wire M923-PU(Purple)).

5. Observe the resistance measurement and wiggle the ECM connector and the sensor connector. Gently pull on the wires and wiggle the wires for both connectors.

Expected Result:

The resistance measurement is less than 5 ohms at all times during the manipulation of the wiring harness and connectors.

Results:

• OK - The resistance measurement is less than 5 ohms. The sensor signal circuit is not open in the machine harness. Proceed to Test Step 3.

• NOT OK - The resistance measurement for the signal circuit is greater than 5 ohms. There is an open or a poor connection in the circuit.

  Repair: Check the signal circuit for opens or for a bad connection.

  A resistance measurement that is greater than 5000 ohms would indicate an open in the circuit. A resistance that is greater than 5 ohms but less than 5000 ohms would indicate the following:

  • A loose connection in the circuit

  • A corroded connection in the circuit
  Refer to the Electrical Schematic of the machine. Check all of the connectors that are in the sensor signal circuit or in the ground circuits. Inspect the connections for the following:

  • Connections are clean.

  • Connections are secure.

  • Connections are in good condition.
  Repair the machine harness or replace the machine harness.

  STOP

Test Step 3. CHECK THE STATUS OF THE DIAGNOSTIC CODE

1. Perform the following:

   • Visually inspect the harness connectors.

   • Clean the contacts of the harness connectors.

   • Visually inspect the insulation of the wires for damage that can be caused by excessive heat, battery acid, or chafing.

2. Perform a 45 N (10 lb) pull test at the connectors that are used in the circuit.

3. Reconnect all harness connectors. Verify the following:

   • The connectors are fully seated.

   • The clips for each connector are fastened.

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

5. Check the status of the CID 2475 FMI 08.

Expected Result:

The CID 2475 FMI 08 is not active.

Results:

• OK - The CID 2475 FMI 08 is not active. The diagnostic code does not exist at this time. The initial diagnostic code could have been caused by a poor connection or short at a connector that was disconnected and reconnected. Resume normal operation

  STOP

• NOT OK - The CID 2475 FMI 08 is active. The diagnostic code has not been corrected.

  Repair: If available, perform a Wiggle Test on the machine wiring harness with the Cat^® Electronic Technician (Cat^® ET) service tool. The Wiggle Test can detect the following in the machine wiring harness:

  • Momentary shorts

  • Intermittent shorts

  • Opens
  If the cause of the active diagnostic code is not found, the ECM may have activated this diagnostic code in error.

  If the cause of the failure is not found, contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may effect repair time.

  If the ECM must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP