120M Series 2, 120M2, 12M Series 2, 12M Series II, 140M Series 2 and 160M Series 2 Motor Graders Implement Electronic Control System Caterpillar

Illustration 1	g02346939
Schematic of the main E/H pump pressure sensor

This diagnostic code is associated with the main pump pressure sensor.

The Implement ECM 2 will activate an FMI 14 for this sensor when the reading of the standby pressure transducer at the discharge side of the hydraulic pump is above 7500 kPa (1089 psi). The output of the pressure sensor is checked by the Implement ECM 2 when the following conditions occur during machine operation:

• Immediately after the engine has been started and the engine low idle speed has been stabilized

• Immediately after the switch for the Secondary Steer Test has been moved to the TEST position

The Implement ECM 2 checks the status of the sensor when a secondary steering test is requested. The ECM checks the sensor status to determine if the sensor is indicating the correct pressure for the secondary steering pump pressure.

The pressure sensor sends a variable voltage input to the ECM that will indicate the main hydraulic pump discharge pressure. The output voltage of the sensor will be around 0.5 VDC when no pressure is applied. The output voltage of the pressure sensor will be around 4.5 VDC at 34500 kPa (5004 psi) of pressure .

The possible conditions that can cause this diagnostic code are listed below:

• A hydraulic problem causing above normal hydraulic pump pressure at start-up or shutdown, with only one sensor installed.

• With two sensors installed, both sensors do not indicate the same pressure.

• The sensor has failed.

• Intermittent or poor harness connections in the sensor supply circuit or the signal circuit.

• The signal circuit for the sensor is shorted to another circuit which is interfering with the sensor signal while still in the accepted range.

• The ECM has failed. This condition is unlikely.

Check that the diagnostic code CID 0262 is not active before performing this procedure. If an active CID 0262 diagnostic code is present, correct the problem and clear the diagnostic code before performing 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.
Refer to Testing and Adjusting, "Electrical Connector - Inspect " in this manual.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the original diagnostic code has been corrected.

Test Step 1. CHECK THE HYDRAULIC PUMP DISCHARGE PRESSURE

Note: This test step requires the installation of a pressure gauge at the tap for the outlet pressure for the main hydraulic pump. Confirm the pressure gauge is properly installed. Then, confirm the pressure gauge displays the expected pressure range, before turning the key start switch to the ON position.

1. After a pressure gauge is installed at the main hydraulic pump pressure tap, start the engine and run the engine at low idle.

2. Ensure that all the following conditions are in place before proceeding to the next step:
   • Disable the steering system by not aligning the joystick to the angle of the front wheels.

   • Disable the steering system by not having the operator in the operator seat.

   • Move the implement lockout switch to the LOCK position.

3. Use Caterpillar Electronic Technician (Cat^® ET) to check the status of the main hydraulic pump pressure.

4. Observe the display of the pressure reading that is on the Cat^® ET status screen. Note the reading on the pressure gauge from the pump outlet. Compare the two sets of readings.

Expected Result:

The pressure is observed on the Cat^® ET status screen and the pressure that is observed on the pressure gauge are approximately the same. However, the pressure reading is above the 7500 kPa (1089 psi) standby pressure limit.

Results:

• YES - The pressure observed on the status screen and the value displayed on the pressure gauge are approximately the same. However, the pressure is above the 7500 kPa (1089 psi) standby pressure limit. There is a problem with the operation of the main hydraulic pump.

  Repair: The standby pressure of the main hydraulic pump is above normal.
  Repeat this test step in order to ensure that all of the listed conditions for testing are correct.
  If the main hydraulic pump standby pressure is still above normal, refer to the machine service manual for more information about troubleshooting the hydraulic pump. See the following manual for your machine model:

  • Testing and Adjusting, KENR8888, "12M Series 2, 140M Series 2 and 160M Series 2 Motor Graders Hydraulic and Steering System"

  • Testing and Adjusting, KENR9458, "120M Series 2 Motor Graders Hydraulic and Steering System"

  STOP

• NO - The pressure value displayed on the Cat^® ET status screen and the value displayed on the pressure gauge are not approximately the same. The Cat^® ET status screen is indicating a higher value than the pressure indicated on the gauge. There is a problem with the pressure sensor or in the circuit of the pressure sensor. Proceed to Test Step 2.

Test Step 2. CHECK THE SENSOR

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

2. Disconnect the machine harness connector from the pressure sensor.

3. Turn the key start switch to the ON position. Do not start the engine.

4. Observe the status of the active diagnostic code for the sensor.

Expected Result:

The active CID 2828 FMI 14 diagnostic changes to an active CID 2828 FMI 03 diagnostic, after disconnecting the sensor from the harness.

Results:

• OK - The active CID 2828 FMI 14 diagnostic changed to an active CID 2828 FMI 03 diagnostic after disconnecting the sensor from the harness. The sensor is causing the problem.

  Repair: Replace the main hydraulic pump discharge pressure sensor. After the sensor is replaced, verify that the problem has been corrected before operating the machine.

  STOP

• NO - The status of the active CID 2828 FMI 14 diagnostic code did not change when the sensor was disconnected from the machine harness. The sensor is not causing the problem. Proceed to Test Step 3.

Test Step 3. CHECK THE SENSOR CIRCUIT AT THE ECM

The key start switch remains in the ON position. The engine is not running.

1. Reconnect the machine harness connector to the pressure sensor. Verify that the CID 2828 FMI 14 diagnostic code is active.

2. At the machine harness connector for the Implement ECM 2 J1, use a 151-6320 Removal Tool to remove the signal wire N931-GY and the socket at contact J1-36 from the J1 connector. The machine harness connector J1 remains connected to the Implement ECM 2.

3. Observe the status of the CID 2828 FMI 14 diagnostic code after the signal wire is removed from the J1 connector.

Expected Result:

The CID 2828 FMI 14 diagnostic changed to a CID 2828 FMI 03 diagnostic, after removing the sensor signal wire from the J1 connector.

Results:

• OK - The CID 2828 FMI 14 diagnostic changed to a CID 2828 FMI 03 diagnostic after removing the sensor signal wire from the J1 connector. The ECM is not the cause of the problem.
  
  Reconnect the signal wire and the socket in the machine harness connector J1 for the ECM before proceeding to the next test step.
  Proceed to Test Step 4.

• NO - The CID 2828 FMI 14 diagnostic did not change when the sensor signal wire was removed from the J1 ECM connector. The ECM may have failed.

  Repair: Reconnect the signal wire and the socket in the machine harness connector J1 for the ECM. Repeat this test step in order to verify that the ECM is the cause of the problem.
  If the ECM is still activating the CID 2828 FMI 14 diagnostic after removing the sensor signal wire from the J1 connector: Implement ECM 2 has failed.
  Prior to replacing an ECM, contact the Technical Communicator (TC) at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time.
  If the ECM requires replacement, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP

Test Step 4. CHECK THE SIGNAL CIRCUIT OF THE SENSOR FOR A SHORT

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

2. Disconnect the machine harness connector from the sensor.

3. Disconnect the machine harness connector J1 and J2 from the Implement ECM and from the Implement ECM 2.

4. At the harness connector J1 for the Implement ECM 2, measure the resistance from signal contact J1-36 (wire N931-GY) to all of the other contacts that are used for the J1 and J2 connectors on the Implement ECM and the Implement ECM 2.

Expected Result:

Each resistance measurement is greater than 5000 ohms.

Results:

• OK - Each resistance measurement is greater than 5000 ohms. The signal circuit is not shorted to another circuit in the machine harness. Proceed to Test Step 5.

• NO - One or more of the resistance measurements is less than 5000 ohms. There is a short in the machine harness.

  Repair: The signal wire of the sensor N931-GY is shorted to the circuit with the low resistance measurement in the machine harness. Refer to the complete Electrical System Schematic of the machine. Examine all of the connectors in the circuits for potential shorted locations in the machine harness.
  For information on testing for short circuits and finding short circuits, refer to Testing and Adjusting, "Wiring Harness (Short Circuit) - Test" in this manual. Repair or replace the machine harness.

  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 is caused by excessive heat, battery acid, or chafing.

   Reference Testing and Adjusting, "Electrical Connector - Inspect " in this manual.

2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the sensor circuit.

3. Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are fastened completely.

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

5. Operate the machine.

6. Determine if the CID 2828 FMI 14 diagnostic code is active.

Expected Result:

The CID 2828 FMI 14 diagnostic code is not active.

Results:

• YES - The CID 2828 FMI 14 diagnostic code is not active. The problem has been corrected.

  Repair: The initial diagnostic code was probably caused by a poor electrical connection that was resolved when a connector was disconnected and reconnected. Resume normal machine operation.

  STOP

• NO - The CID 2828 FMI 14 diagnostic code is still active. The problem has not been corrected.

  Repair: Perform this test step again.
  If the problem has not been corrected, proceed with the following process. Use Cat^® ET and perform a wiggle test on the sensor circuit for the machine wiring harness of the machine. The wiggle test can be used to detect momentary short circuit and open connections in the machine wiring harness.
  If a problem is not found in the machine harness, replace the pressure sensor. If the problem is still present after replacement of the sensor, the Implement ECM 2 may have failed. Prior to replacing an ECM, contact the Technical Communicator (TC) at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time.
  If the cause of the diagnostic code is not found, replace the Implement ECM 2.
  Refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace" in this manual.

  STOP