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	g02102716
Connections of the spool position sensor for the steering valve control module

This diagnostic code is associated with the spool position sensor for the steering valve control module. The code is recorded when the Implement ECM 2 records an erratic signal or an intermittent signal from the spool position sensor. The position sensor provides an input to the Implement ECM 2. The FMI 02 diagnostic code is activated when the ECM detects an input signal that is erratic, intermittent, or incorrect from the sensor.

The following conditions could cause this diagnostic code to be activated:

• The signal circuit is intermittently open.

• A signal circuit is shorted.

• The signal circuit is intermittently shorted to ground.

• The signal circuits may be intermittently shorted together.

• The ECM has failed.

• Mechanical devices are loose.

• There is an intermittent connection in the sensor circuit.

• Opens in the sensor circuit

• The sensor has failed.

• The ECM has failed. This condition is unlikely.

The spool position sensor for the steering valve control module supplies an analog voltage signal to the ECM in order to indicate the position of the valve spool in the steering control module. The signal voltage varies from 1.25 VDC to 3.75 VDC. When the joystick is stationary and the spool is in the center position, a signal voltage of approximately 2.5 VDC will be supplied to the ECM.

The following conditions could cause this diagnostic code to be activated:

Note: The Implement ECM 2 supplies power for the control module of the steering valve through an ON/OFF driver at contact J1-12. Before performing this procedure, check for an active CID 2650 diagnostic code. Correct any problem with the power supply before performing this procedure.

Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections are often 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.

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. Clear the diagnostic codes when the original diagnostic code has been corrected.

Test Step 1. CHECK THE VOLTAGE OF THE SENSOR SIGNAL AT THE SENSOR

Note: Certain conditions that can cause the Implement ECM 2 to activate the CID 2203 FMI 02 diagnostic code can also cause the Implement ECM 2 to activate the CID 2202 FMI 12 (steering valve which is the bad component). When this occurs, the ECM will turn OFF the output that supplies power to the control module of the steering valve at contact J1-12. If the CID 2202 FMI 12 diagnostic code is active, it is not possible to check the voltages of any of the control signals. In this test step, the ECM that has the erratic signal is shorted to ground. Short the pin to ground in order to supply power to the control module of the steering valve if the CID 2202 FMI 12 diagnostic code is active.

1. Verify that a CID 2202 FMI 12 diagnostic code is active. If a CID 2202 FMI 12 diagnostic code is active, proceed to the next step. If the CID 2202 FMI 12 diagnostic code is not active, proceed to step "F".

2. At the machine harness connector J1 for the Implement ECM 2, use a 151-6320 Removal Tool to remove the wire U742-WH and the socket at contact J1-40 from the harness connector. Wire U742-WH has the erratic signal. The J1 connector remains connected to the Implement ECM 2.

3. With a 7X-1710 Multimeter Probe that is not connected to a multimeter or with a similar jumper wire, connect one end to the ECM pin at J1-40 through the empty space in the J1 connector.

4. Connect the other end of the jumper wire to frame ground. This probe or jumper wire must remain connected during the rest of this procedure.

5. Turn the disconnect switch to the ON position.

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

7. If the jumper wire is connected to frame ground and the ECM pin J1-40, the CID 2202 FMI 12 diagnostic code is not active.

8. At the machine harness connector for the steering control module, use a 151-6320 Removal Tool to remove the signal wire U736-YL and the socket at contact 4 from the harness connector. The machine harness connector remains connected to the control module of the steering valve.

9. Start the engine. Run the engine at low idle speed.

10. Enable the steering system. The steering system must be enabled in order to check the signal voltage.

11. At the harness connector for the control module of the steering valve, insert a 7X-1710 Multimeter Probe along return contact 5 (wire H808-WH). Insert the other multimeter probe through the empty space at contact 4 in order to contact the pin on the connector of the control module of the steering valve.

12. While moving the left joystick to various steering positions, measure the voltage between contact 4 and contact 5.

Expected Result:

The voltage measurement is in the range that is described at the beginning of this procedure.

Results:

• OK - The voltage measurement is in the range that is described at the beginning of this procedure. The signal voltage of the position sensor for the spool is correct. Before proceeding to the next test step, connect the signal wire U736-YL and the socket back into contact 4 of the harness connector for the control module of the steering valve. Proceed to Test Step 2.

• NOT OK - The voltage measurement is not in the range that is described at the beginning of this procedure. The signal voltage is not correct.

  Repair: Verify that there are no active CID 2202 or CID 2650 diagnostic codes and that the steering system is enabled.Verify that the multimeter probes are making good connections on return contact 5 and on the contact 4 at the connector for the control module of the steering valve. Measure the voltage of the signal again.If the voltage measurement is not in the correct range, the steering control module may have failed.Prior to replacing the control module of the steering valve, contact the Technical Communicator at your dealership for possible consultation with Caterpillar.

  STOP

Test Step 2. CHECK THE VOLTAGE OF THE SENSOR SIGNAL AT THE ECM

1. The jumper wire that is connected between frame ground and the contact J1-40 of the Implement ECM 2 remains connected.

2. Turn the disconnect switch to the OFF position.

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

4. At the back of the J1 harness connector for the Implement ECM 2, insert 7X-1710 Multimeter Probes along signal contact J1-37 (wire U736-YL) and along return contact J2-4 (wire H808-WH).

5. Turn the disconnect switch to the ON position.

6. Start the engine. Run the engine at low idle speed.

7. Enable the steering system. The steering system must be enabled in order to check the signal voltage.

8. While moving the left joystick to various steering positions, measure the voltage between contact J1-37 and contact J2-4.

Expected Result:

The voltage measurement is in the range that is described at the beginning of this procedure.

Results:

• OK - The voltage measurement is in the range that is described at the beginning of this procedure. The signal voltage of the position sensor for the spool is correct. Before proceeding to the next test step, if a jumper wire was connected, remove the jumper wire and reconnect the wire that has the erratic signal back to the correct location at the ECM connector J1-40. Proceed to Test Step 5.

• NOT OK - The voltage measurement is not in the range that is described at the beginning of this procedure. The signal voltage is not correct. Before proceeding to the next test step, if a jumper wire was connected, remove the jumper wire and reconnect the wire that has the erratic signal back to the correct location at the ECM connector J1-40. Proceed to Test Step 3.

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

1. Turn the disconnect switch to the OFF position.

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

3. Disconnect the machine harness connector from the control module of the steering valve.

4. At the machine harness connector for the control module of the steering valve, place a jumper wire between return contact 5 (wire H808-WH) and signal contact 4 (wire U736-YL).

5. Disconnect the machine harness connectors J1 and J2 from the Implement ECM 2.

6. At the Implement ECM 2, measure the resistance from return contact J2-4 (wire H808-WH) to signal contact J1-37 (wire U736-YL).

Expected Result:

The resistance is less than 5 ohms.

Results:

• OK - The resistance is less than 5 ohms. The signal circuit is not open. Proceed to Test Step 4.

• NOT OK - The resistance is greater than 5 ohms. There is an open or a bad connection in the signal circuit of the Implement ECM 2.

  Repair: A resistance measurement that is greater than 5000 ohms could indicate that a wire is not connected or a wire is open. A resistance measurement that is greater than 5 ohms but less than 5000 ohms could indicate that one of the connection points in the circuit is not completely open, but the connection is poor.Refer to the Electrical Schematic of the machine. In the suspected circuit, verify the following:

  • Connections are clean.

  • Connections are secure.

  • Connections are in good condition.

  Check the connector that passes the wires through the bulkhead at the front of the cab. In the suspected circuit, verify the following:
  • Connections are clean.

  • Connections are secure.

  • Connections are in good condition.

  Repair the machine harness or replace the machine harness.

  STOP

Test Step 4. CHECK THE SIGNAL CIRCUIT FOR A SHORT

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

2. The machine harness connectors J1 and J2 for the Implement ECM 2 remain disconnected.

3. The machine harness connector remains disconnected from the control module of the steering valve.

4. At the J1 machine harness connector for the Implement ECM 2, measure the resistance from the signal contact J1-37 (wire U736-YL) to all of the other J1 and J2 contacts that are used on 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 resistance measurements are not indicating that there is a short in the circuit. Proceed to Test Step 6.

• NOT OK - One or more resistance measurements are less than 5000 ohms. The signal circuit is shorted to another circuit.

  Repair: There is a short in the machine harness. The short is between the signal wire U736-YL and the circuit with the low resistance.Refer to the Electrical Schematic of the machine. Examine all of the connectors in circuits for points that could be shorted in the machine harness. For information on testing for short circuits and finding short circuits, refer to the Testing and Adjusting, "Wiring Harness (Short Circuit) - Test" Story in this manual. Repair the machine harness or replace the machine harness.

  STOP

Test Step 5. CHECK THE OPERATION OF THE ECM

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

2. Reconnect the machine harness connector to the control module of the steering valve.

3. Reconnect the machine harness connectors J1 and J2 to the Implement ECM 2.

4. At the machine harness connector J1 for the ECM, use a 151-6320 Removal Tool to remove the signal wire U736-YL and the socket at contact J1-37 from the harness connector. The J1 connector remains connected to the ECM.

5. Turn the disconnect switch to the ON position.

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

7. With a 7X-1710 Multimeter Probe that is not connected to a multimeter, connect the ECM pin at J1-37 through the empty space in the J1 connector.

8. While the status of the active CID 2203 FMI 03 diagnostic code is observed, ground the other end of the 7X-1710 Multimeter Probe to frame ground.

Expected Result:

The CID 2203 FMI 03 diagnostic code is no longer active. A CID 2203 FMI 04 diagnostic code becomes active when the ECM pin at J1-37 is grounded.

Results:

• OK - The CID 2203 FMI 02 diagnostic code is no longer active. A CID 2203 FMI 04 diagnostic code has been activated after the ECM pin is grounded. The ECM has responded correctly to the grounded circuit condition. The ECM is not causing the problem. Reconnect the signal wire in the ECM connector before proceeding to the next test step. Proceed to Test Step 6.

• NOT OK - The CID 2203 FMI 02 diagnostic code remains active. The status of the active diagnostic code does not change when the ECM pin for the circuit of the spool position sensor is grounded.

  Repair: The ECM has not responded correctly to the grounded condition in the circuit. The operation of the ECM is not correct.The ECM may have failed. However, it is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM must be replaced, refer to the Testing and Adjusting, "Electronic Control Module (ECM) - Replace" Story in this manual.

  STOP

Test Step 6. 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 is caused by excessive heat, battery acid, or chafing.

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. Verify the following:
   • Connectors are fully seated.

   • The clips for each connector are fastened completely.

4. Turn the disconnect switch to the ON position.

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

6. Operate the machine.

7. Check the status of the CID 2203 FMI 02 diagnostic code.

Expected Result:

The CID 2203 FMI 02 diagnostic code is not active.

Results:

• OK - The CID 2203 FMI 02 diagnostic code is not active. The diagnostic code does not exist at this time. The initial diagnostic code was probably 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 2203 FMI 02 diagnostic code is active. The diagnostic code has not been corrected.

  Repair: Check the circuit again. 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 Implement ECM 2 may have failed.It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. Prior to replacing an ECM, always contact the Technical Communicator 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 ECM that has activated the diagnostic code. Refer to the Testing and Adjusting, "Electronic Control Module (ECM) - Replace" Story in this manual for additional information.

  STOP