950K and 962K Wheel Loaders Electrohydraulic System Caterpillar

Illustration 1	g02428679
(1) Lift Cylinder Head End Pressure Sensor located on the small manifold that is mounted under the sampling ports on the right side of the machine. View: From the machine left side. In front of the articulation hitch looking toward the right side of the non-engine end frame.

Illustration 2	g02428677
Connections of the Lift Cylinder Head End Pressure Sensor

This diagnostic code is associated with the Lift Cylinder Head End Pressure 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.

The Lift Cylinder Head End Pressure Sensor receives power from the 8V power supply of the Implement ECM. The sensor is connected to ground from the 8V sensor return for the Implement ECM. The illustration above indicates the power and ground connections for the pressure sensor.

The sensor is a 50 MPa (7252 psi) rated pressure sensor that operates at approximately 500 Hz. The pressure sensor sends a PWM input signal to the ECM. The duty cycle of the signal will vary from 5% to 95%.

If the ECM detects the frequency is less than 400 Hz or greater than 600 Hz, an FMI 08 code will be activated.

The following table indicates the sensor PWM duty cycles at the given oil pressures.

The possible causes of this diagnostic code are listed below:

• The sensor has failed.

• Intermittent connections or poor connections

• The ECM has failed. This condition is unlikely.

Note: If a CID 0041 diagnostic code for the 8V power supply has been activated, correct the problem before proceeding with this procedure.

Note: Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Inspect the connections for the following:

• Connections are clean.

• Connections are secure.

• Connections are in good condition.

Note: If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the problem 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 pressure sensor, use a 151-6320 Removal Tool to remove the signal wire Y791-BU(Blue) and the socket at contact 3 from the harness connector. The machine harness connector remains connected to the pressure sensor.

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

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

5. With the lift cylinder in the stationary condition, measure the frequency of the signal from the sensor.

6. Observe the measurement and wiggle the pressure sensor connector. 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. Check that the pressure sensor is within range according to the description at the beginning of this procedure.

Expected Result:

The frequency of the lift cylinder head end pressure sensor signal is 500 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 lift cylinder head end pressure sensor is not correct. Replace the pressure 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 pressure sensor. At machine harness connectors, place a jumper wire between the signal contact 3 (wire Y791-BU(Blue)) and frame ground.

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

4. Observe the status of the active CID 0364 FMI 08 diagnostic code.

Expected Result:

The active diagnostic code CID 0364 FMI 08 is no longer active. A CID 0364 FMI 04 diagnostic code becomes active when the signal wire (Y791-BU(Blue)) is grounded.

Results:

• YES - The active diagnostic code CID 0364 FMI 08 is no longer active. A CID 0364 FMI 04 diagnostic code has been activated after the signal wire is grounded. Proceed to Test Step 3.

• NO - The CID 0364 FMI 08 diagnostic code remains active. The status of the active diagnostic code does not change when the signal wire is grounded. There is an open or a poor connection in the signal wire.

  Repair: Check the signal circuit for an open or for a poor connection. Repair 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 0364 FMI 08.

Expected Result:

The CID 0364 FMI 08 is not active.

Results:

• OK - The CID 0364 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 a short at one of the connectors that was disconnected and reconnected. Resume normal operation

  STOP

• NOT OK - The CID 0364 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 Caterpillar 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 that has activated this diagnostic code may have failed.

  Exit this procedure and perform this procedure again. 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