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 code is recorded when the ECM reads the input signal from the Lift Cylinder Head End Pressure Sensor and the voltage is above normal.

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 PWM duty cycle or voltage of a sensor input circuit is greater than 97%, an FMI 03 diagnostic 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:

• The power supply circuit of the sensor is open.

• The return circuit of the sensor is open.

• The signal circuit is open.

• The signal circuit is shorted to the sensor power supply.

• The sensor has failed.

• 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. Verify that all connections in the circuit are clean, that all connections are secure and that all connections are in good condition. 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 POWER SUPPLY OF THE SENSOR CIRCUIT

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

2. At the pressure sensor harness connector, insert 7X-1710 Multimeter Probes along the power supply contact 1 (wire A105-OR(Orange)) and along ground contact 2 (wire X719-OR(Orange)).

3. Do not disconnect the machine harness from the connector.

4. Measure the DC voltage of the sensor power supply.

Expected Result:

The voltage measurement is approximately 8.0 ± 0.4 DCV.

Results:

• OK - The voltage measurement is approximately 8.0 ± 0.4 DCV. The power supply for the sensor is correct. Proceed to Test Step 2.

• NOT OK - The voltage measurement is less than 8.0 ± 0.4 VDC. The power supply for the sensor is not correct.

  Repair: If the voltage measurement is not correct, the problem is most likely in the power supply circuit. This condition will cause multiple diagnostic codes to activate.

  Refer to the complete Electrical System Schematic of the machine. Examine all of the connectors that are in the circuits. Ensure that the connections are clean, that all connections are secure and that all connections are in good condition.

  For troubleshooting the ECM power supply that is providing power to the sensor, refer to the CID 0041 diagnostic code procedures.

  Repair the faulty power supply circuit before proceeding with this procedure.

  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 the harness connector for the pressure sensor, place a jumper wire between the signal contact J1-10 (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 03 diagnostic code.

Expected Result:

The active diagnostic code CID 0364 FMI 03 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 03 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 03 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 SIGNAL CIRCUIT FOR A SHORT

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

2. Remove the jumper wire that was installed in the last step.

3. At the J2 machine harness connector for the ECM, measure the resistance between the sensor signal contact J2-49 (wire Y791-BU(Blue)) and each of the other J1 and J2 circuits that are used for the Implement ECM.

Expected Result:

Each resistance measurement is greater than 5000 ohms.

Results:

• OK - Each resistance measurement is greater than 5000 ohms. The resistance measurements do not indicate a short in the circuit. Proceed to Test Step 4.

• NOT OK - A resistance measurement is less than 5000 ohms.

  Repair: There is a short in the machine harness. The short is between the signal circuit and the circuit with the low resistance measurement.

  Refer to the complete Electrical System Schematic of the machine. Check all of the connectors that are in the sensor circuit. Ensure that all connections are clean, that all connections are secure and that all connections are in good condition.

  For information on testing for short circuits and finding short circuits, refer to Testing and Adjusting, "Wiring Harness (Short Circuit) - Test". Repair the machine harness or replace the machine harness.

  STOP

Test Step 4. CHECK THE SIGNAL AT THE SENSOR

The key start switch and the disconnect switch remain in the OFF position.

1. Inspect all of the harness connectors for the pressure sensor and the ECM. Clean the contacts of the harness connectors and check the wires for damage to the insulation. Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are fastened.

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. Measure the duty cycle of the sensor at the connector pins of the sensor 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 duty cycle of the sensor is correct according to the description at the beginning of this procedure.

Results:

• OK - The duty cycle of the sensor is correct. The sensor is not the cause of the problem. Reconnect the signal wire and the socket in the machine harness connector for the pressure sensor. Proceed to Test Step 5.

• NOT OK - 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.

  If the pressure sensor is not correct according to the description at the beginning of this procedure, replace the sensor. After replacement of the sensor, verify that the operation of the new sensor is correct before operating the machine.

  STOP

Test Step 5. CHECK THE STATUS OF THE DIAGNOSTIC CODE

1. Inspect the harness connectors. Clean the contacts of the harness connectors. Check the wires for damage to the insulation 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 sensor circuit.

3. Reconnect all harness connectors. Make sure that the connectors are fully seated and locked.

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

5. Determine if the CID 0364 FMI 03 diagnostic code is active.

Expected Result:

The CID 0364 FMI 03 diagnostic code is not active.

Results:

• OK - The CID 0364 FMI 03 diagnostic code 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 03 diagnostic code 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