14L Motor Grader Implement Electronic Control System Caterpillar

Illustration 1	g03171003
Connections of "Steer Sensor 3"

Three "steer position sensors" are required for correct operation of the steering control. The "steer position sensors" are located in the assembly of the left joystick . Each sensor provides an input signal to the Implement ECM and to the Transmission/Chassis ECM. This diagnostic code is recorded when the ECM reads the input signal from the "steer position sensor 3" and the signal is erratic or intermittent.

The "steer position sensor 3" receives power from the 8V power supply of the Transmission/Chassis ECM. The "steer sensor 3" is internally connected to the ground from the 5V sensor return of the Transmission/Chassis ECM and to the Implement ECM (ground of ECM). The "steer sensor" must lose the 8V power supply or both grounds in order to lose power. The illustration above indicates the power and ground connections for "steer position sensor 3".

Note: For a schematic of the internal power and ground assignments for each individual component in the left joystick, refer to the Systems Operation, "Features" section of this manual.

The position sensor is a PWM sensor that operates at a frequency of approximately 500 Hz. The position sensor sends a PWM input signal to the Implement ECM and to the Transmission/Chassis ECM. The duty cycle of the signal will vary from approximately 10 ± 5% at the full left position of the joystick to approximately 90 ± 5% at the full right position of the joystick. When the joystick is in the center position, the duty cycle will be approximately 50%.

The possible causes of this diagnostic code are listed below:

• The sensor has failed.

• Intermittent connections or poor connections exist in the sensor circuit.

• The signal circuit is shorted to another circuit in the machine harness.

• The ECM has failed. This is unlikely.

Consider the following points when this code is active:

Note: Before performing this procedure, check for an active MID 027 CID 0041 diagnostic code for the 8V sensor power supply of the Transmission/Chassis ECM. Correct any problem with the 8V power supply before performing this procedure.

Note: The Transmission/Chassis ECM (MID 027) and the Implement ECM (MID 082) receive an input signal from the "steer sensor 3". Both ECM modules can activate a CID 1473 FMI 02 diagnostic code when the signal is erratic or intermittent. If one ECM has activated a CID 1473 FMI 02 diagnostic code and the other ECM has not activated a CID 1472 FMI 02, it is likely that the sensor is operating correctly. When this occurs, a poor connection in the machine harness would be suspected. When both ECM modules have activated the diagnostic code, either the sensor OR a harness problem could be the cause. If both ECM modules have activated the diagnostic code, it is very unlikely that either ECM is causing the problem. For either condition, proceed with this procedure in order to verify the cause of the problem.

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 the connections are secure and that the 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 SENSOR POWER SUPPLY

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

2. At the machine harness connectors for the left joystick, insert 7X-1710 Multimeter Probes along the contact for the power supply J3-2 (wire T998-BR(Brown)) and along ground 1 contact J1-3 (wire L731-BR(Brown)). Do not disconnect the machine harness from the connectors of the joystick.

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

4. Reposition the multimeter probe that is along the contact for ground 1 J1-3 (wire L731-BR(Brown)) to along the contact for ground 4 J3-3 (wire 998-BR(Brown)). The other multimeter probe remains positioned along the contact for the power supply J3-2 (wire T998-BR(Brown)).

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

Expected Result:

Both of the voltage measurements are approximately 8.0 ± 0.4 VDC.

Results:

• OK. - Both of the voltage measurements are approximately 8.0 ± 0.4 VDC. The power supply of the Transmission/Chassis ECM for the sensor is correct. Proceed to Test Step 2.

• NOT OK. - One or both of the voltage measurements is not 8.0 ± 0.4 VDC. The power supply for the Transmission/Chassis ECM for the sensor is not correct.

  Repair: Either both of the wires of the ground circuit for the sensor are faulty or the sensor supply circuit is faulty.

  NOTE: If one of the voltage measurements is correct and the other measurement is not correct, one of the ground circuits is faulty. This condition will not cause this code to be active. However, the faulty ground circuit must be repaired before proceeding with this procedure.

  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 the connectors are secure and that the connectors are in good condition.

  For troubleshooting the power supply of the Transmission/Chassis ECM , refer to the CID 0041 diagnostic code procedures in the troubleshooting section of the manual for the Transmission/Chassis ECM.

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

  STOP

Test Step 2. CHECK THE SIGNAL AT THE SENSOR

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

1. At the machine harness connector J3 for the left joystick, use a 151-6320 Removal Tool to remove the signal wire U741-OR(Orange) and the socket at contact J3-1 from the harness connector. The machine harness connector J3 remains connected to the connector of the left joystick.

2. At the back of the connectors of the joystick J3 and J1, insert 7X-1710 Multimeter Probes along the contact of the sensor signal J3-1 and the contact for ground 4 at J3-3.

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

4. Measure the duty cycle of the sensor at the connector contacts of the joystick J3-1 and J3-3. Move the joystick through the full range of the sensor that is described at the beginning of this procedure.

Expected Result:

The duty cycle of the "steer sensor 3" 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. Reinstall the signal wire U741-OR(Orange) and the socket back to the original location at contact J3-1 in the machine harness connector for the joystick. Verify that all of the wires of the joystick are in the correct locations. Verify that all the wires of the joystick are secure in the connector before proceeding to the next step. Proceed to Test Step 3.

• NOT OK. - The duty cycle of the "steer sensor 3" 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 "steer sensor 3" signal is not correct according to the description at the beginning of this procedure, replace the assembly of the left joystick. After replacement of the assembly of the joystick, verify that the operation of the assembly of the new joystick is correct before operating the machine.

  STOP

Test Step 3. CHECK THE SIGNAL AT BOTH OF THE ECM MODULES

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

2. At the machine harness connector J1 for the Implement ECM, insert a multimeter probe along return contact J1-21 (998-BR(Brown)). At the machine harness connector J2 for the Implement ECM, insert a multimeter probe along signal contact J2-34 (wire U741-OR(Orange)). The machine harness connectors remain connected to the ECM.

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

4. Measure the duty cycle of the sensor at the connector contacts of the ECM J1-21 and J2-34. Move the joystick through the full range of the sensor that is described at the beginning of this procedure.

5. At the machine harness connector J1 for the Transmission/Chassis ECM, insert a multimeter probe along return contact J1-21 (L731-BR(Brown)). At the machine harness connector J2 for the Implement ECM, insert a multimeter probe along signal contact J2-34 (wire U741-OR(Orange)). The machine harness connectors remain connected to the ECM.

6. Measure the duty cycle of the sensor at the connector contacts of the ECM J1-21 and J2-34. Move the joystick through the full range of the sensor that is described at the beginning of this procedure.

Expected Result:

The duty cycle of the "steer sensor 3" is correct according to the description at the beginning of this procedure at both of the ECM modules.

Results:

• OK. - The duty cycle of the sensor is correct at both of the ECM modules. The machine harness does not appear to be the cause of the problem. An intermittent open or a short circuit could still be causing the problem. Proceed to Test Step 4.

• NOT OK. - The duty cycle of the "steer sensor 3" is NOT correct at one or both of the ECM modules according to the description at the beginning of this procedure. There is a problem in the machine harness.

  Repair: If the sensor signal at one ECM is correct and the sensor signal at the other ECM is not correct, a poor connection in the circuit would be suspected.

  The "steer sensor 3" signal at one of the ECM modules is not correct.

  Refer to the complete Electrical System Schematic of the machine. Examine all of the connectors that are in the section of the sensor signal circuit that connects to the ECM that is not receiving a good signal. Verify that the connections are clean, that all connections are secure and that all connections are in good condition. Repair the machine harness or replace the machine harness.

  STOP

• NOT OK. - The duty cycle of the "steer sensor 3" is NOT correct at either of the ECM modules according to the description at the beginning of this procedure. A problem in the machine harness is the most likely cause. Proceed to Test Step 4.

Test Step 4. CHECK THE SIGNAL CIRCUIT FOR A SHORT

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

1. Disconnect the J1 connector and the J2 connector from the Implement ECM.

2. At the J2 machine harness connector for the Implement ECM, measure the resistance from the sensor signal contact J2-34 (wire U741-OR(Orange)) to all of the other J1 and J2 contacts that are used for the Implement ECM.

3. If any of the resistance measurements in the last test step are less than 5kΩ, skip the next test step and proceed to the “expected result” step. If all of the resistance measurements in the last test step are above 5kΩ, perform the next test step.

4. Disconnect the J1 connector and the J2 connector from the Transmission/Chassis ECM.

5. At the J2 machine harness connector for the Transmission/Chassis ECM, measure the resistance from the sensor signal contact J2-34 (wire U741-OR(Orange)) to all of the other J1 and J2 contacts that are used for the Transmission/Chassis ECM.

Expected Result:

Each resistance measurement is greater than 5kΩ.

Results:

• OK. - Each resistance measurement is greater than 5kΩ. The resistance checks of the signal circuit do not indicate a short in the machine harness. Proceed to Test Step 5.

• NOT OK. - A resistance measurement is less than 5kΩ.

  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 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.

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 completely fastened.

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

5. Operate the machine.

6. Determine if the CID 1473 FMI 02 diagnostic code is active.

Expected Result:

The CID 1473 FMI 02 diagnostic code is not active.

Results:

• OK. - The CID 1473 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 1473 FMI 02 diagnostic code is active. The diagnostic code has not been corrected.

  Repair: Check the circuit again. Use the Caterpillar Electronic Technician (ET) service tool, if available, in order to perform a wiggle test on the machine wiring harness. The wiggle test can detect momentary shorts or intermittent shorts. The wiggle test can also be used to detect open connections in the machine wiring harness.

  If the cause of the active diagnostic code is not found, the ECM that has activated the diagnostic code may have failed.

  If both the Transmission/Chassis ECM and the Implement ECM have activated this diagnostic code, it is very unlikely that either ECM is causing the problem.

  Exit this procedure and perform this procedure again. If the cause of the failure is not found, contact the Technical Communicator of your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time.

  If the ECM must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP