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 below 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 less than 3%, an FMI 04 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 signal circuit is shorted to ground.

• 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. 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 SENSOR

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

2. Disconnect the machine harness connector from the pressure sensor. Observe the status of the active CID 0364 FMI 04 diagnostic code.

Expected Result:

The status of the CID 0364 FMI 04 diagnostic code did not change when the pressure sensor was disconnected. A CID 0364 FMI 03 diagnostic code has not been activated by the ECM. The CID 0364 FMI 04 diagnostic code remains active when the pressure sensor is disconnected.

Results:

• OK - The CID 0364 FMI 04 diagnostic code remains active when the pressure sensor is disconnected. The sensor is not the cause of the problem. Proceed to Test Step 2.

• NOT OK - The CID 0364 FMI 04 diagnostic code is no longer active when the pressure sensor is disconnected. A CID 0364 FMI 03 diagnostic code is activated by the ECM when the pressure sensor is disconnected. The machine harness and the ECM are operating correctly.

  Repair: The operation of the sensor is the cause of the problem. Replace the lift cylinder head end pressure sensor. After replacement of the sensor, verify that the operation is correct before operating the machine.

  STOP

Test Step 2. CHECK THE SIGNAL CIRCUIT FOR A SHORT TO GROUND

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

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

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

4. At machine harness connector J2 for the ECM, measure the resistance between contact J2-49 (wire Y791-BU(Blue)) and frame ground and measure the resistance to 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 machine harness is correct. Proceed to Test Step 3.

• NOT OK - One or more of the resistance measurements is not correct. The machine harness has failed.

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

  Refer to the Electrical Schematic of the machine. Check all of the connectors that are in the sensor circuit. Check all of the connectors that are in the sensor circuit. Inspect the connections for the following:

  • Connections are clean.

  • Connections are secure.

  • 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 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 sensor 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. Determine if the CID 0364 FMI 04 diagnostic code is active.

Expected Result:

The CID 0364 FMI 04 diagnostic code is not active.

Results:

• OK - The CID 0364 FMI 04 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 04 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