950K and 962K Wheel Loaders Electrohydraulic System Caterpillar

Illustration 1	g02683996
Schematic of the Implement Pump Discharge Pressure Sensor

This diagnostic code is recorded when the Implement ECM determines that the signal from the Implement Pump Discharge Pressure Sensor is incorrect.

The possible causes of this diagnostic code are listed:

• The signal circuit is open.

• The +battery circuit from the electrical system to the sensor is open.

• The signal circuit is shorted to the +battery circuit.

• The signal circuit is shorted to ground.

Note: Ensure that the diagnostic code is active.

Test Step 1. CHECK THE VOLTAGE FROM THE SIGNAL CIRCUIT

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

2. Disconnect the machine harness from the pressure sensor.

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

4. At the harness connector for the pressure sensor, measure the voltage between contact 2 (wire X719-OR(Orange)) and contact 3 (wire K904-GN(Green)).

Expected Result:

The voltage is 8 ± .8 VDC.

Results:

• YES - The voltage is 8 ± .8 VDC. The voltage is correct. Proceed to Test Step 5.

• NO - The voltage is not 8 ± .8 VDC. The voltage is not correct. Proceed to Test Step 2.

Test Step 2. CHECK THE +BATTERY VOLTAGE

1. Ensure that the key start switch is in the ON position.

2. At the harness connector for the sensor, measure the voltage between contact 1 (wire A105-OR(Orange)) and contact 2 (wire X719-OR(Orange)).

Expected Result:

The voltage is between 18 VDC and 24 VDC.

Results:

• YES - The voltage is between 18 VDC and 24 VDC. The voltage is correct. Proceed to Test Step 3.

• NO - The voltage is less than 18 VDC. The voltage is not correct. There may be an open or a short in the machine harness.

  Repair: Repair the harness or replace the harness.

  STOP

Test Step 3. CHECK FOR AN OPEN IN THE SIGNAL CIRCUIT

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

2. Disconnect the connector for the ECM.

3. The machine harness from the pressure sensor remains disconnected.

4. Measure the resistance between contact 3 (wire K904-GN(Green)) at the connector for the pressure sensor and contact J2-33 at the connector for the ECM.

Expected Result:

The resistance should measure less than 5 Ohms.

Results:

• YES - The resistance is less than 5 Ohms. The resistance is correct. Proceed to Test Step 4.

• NO - The resistance is greater than 5 Ohms. The resistance is not correct.

  Repair: Repair the harness or replace the harness.

  STOP

Test Step 4. CHECK FOR A SHORT IN THE SIGNAL CIRCUIT

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

2. At the connector for the ECM, measure the resistance between contact J2-33 (wire K904-GN(Green)) and the other contacts that are in the connector for the ECM.

Expected Result:

The resistance is greater than 5000 Ohms.

Results:

• YES - The resistance is greater than 5000 Ohms. The resistance is correct. Proceed to Test Step 5.

• NO - The resistance is less than 5000 Ohms. The resistance is not correct. There is probably a short in the signal circuit for the machine harness.

  Repair: Repair the harness or replace the harness.

  STOP

Test Step 5. CHECK THE FREQUENCY OF THE PRESSURE SENSOR

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

2. Connect the machine harness to the pressure sensor.

3. The machine harness remains disconnected from the ECM.

4. Install a 8T-0859 Pressure Gauge and the proper Diagnostic Hose on the pressure tap for the sensor. Route the diagnostic hose and the pressure gauge into the cab.

5. Connect a 9U-7330 Digital Multimeter or a 8T-5201 Generator and Counter Signal Group between frame ground (wire X719-OR(Orange)) and contact J2-33 (wire K904-GN(Green)) to the connector of the ECM.

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

7. At the connector for the ECM, Measure the frequency of the pressure sensor with zero pressure at the cylinder.

8. Raise the lift arms until the pressure on the gauge reads 20700 kPa (3000 psi). When the pressure gauge reads 20700 kPa (3000 psi) observe the frequency displayed on the digital multimeter.

Expected Result:

The frequency is between approximately 200 ± 20 Hz at 0 kPa (0 psi). The frequency should be approximately 800 ± 30 Hz at a pressure of 20700 kPa (3000 psi).

Results:

• YES - The frequency is approximately 200 ± 20 Hz at a pressure of 0 kPa (0 psi). The frequency is approximately 800 ± 30 Hz at a pressure of 20700 kPa (3000 psi).

  Repair: The sensor is functioning properly. It is unlikely that the ECM has failed. Perform the previous steps again. If the cause of the problem is not found, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP

• NO - The frequency is not approximately 200 ± 20 Hz at 0 kPa (0 psi). The frequency is not at 800 ± 30 Hz at a pressure of 20700 kPa (3000 psi). The pressure sensor has failed.

  Repair: Replace the pressure sensor.

  STOP