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 associated with the steering position sensor 3. The FMI 08 means that the ECM has detected that the signal frequency or the signal pulse width is not within the expected range.

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 500 ± 100 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 in the sensor circuit or poor connections in the sensor circuit

• 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 correct operating temperature range for the steering sensors is −40 °C (−40.0 °F) to 75 °C (167.0 °F). If an FMI 03 or an FMI 08 diagnostic code becomes active for a steering sensor when the cab environment is at extreme temperatures, normalize the cab environment in order to keep the steer sensors operating in the acceptable temperature range. After temperature normalization, verify that the CID 1473 FMI 08 diagnostic code is active 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 08 diagnostic code when the ECM has detected that the signal frequency or the signal pulse width is not within the expected range. If one ECM has activated a CID 1473 FMI 08 diagnostic code and the other ECM has not activated a CID 1473 FMI 08, 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 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 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.

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 DUTY CYCLE AND THE SIGNAL FREQUENCY AT THE SENSOR

Turn the key start switch and the disconnect switch to 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 (wire U741-OR(Orange)) and the socket at contact J3-1. 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 sensor signal contact J3-1 and the ground 4 contact at J3-3.

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

4. With the joystick in a stationary position, measure the frequency of the signal from the sensor.

5. Observe the measurement and wiggle the connector of the joystick. Gently pull on the wires and wiggle the wires.

6. 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.

7. Observe the measurement and wiggle the connector of the joystick. Gently pull on the wires and wiggle the wires.

Expected Result:

The frequency of the "steer sensor 3" signal is 500 ± 100 Hz. The duty cycle of the "steer sensor 3" is correct according to the description at the beginning of this procedure. The frequency and the duty cycle are stable during the manipulation of the harness connector and the wiring.

Results:

• OK. - The signal frequency of the sensor and the duty cycle of the sensor are correct. The signal frequency and the duty cycle do not change when the harness is manipulated. The sensor is not causing the problem. Reconnect the signal wire and the socket in the machine harness connector for the joystick. Verify that all of the wires of the joystick are secure in the connector before proceeding to the next step. Proceed to Test Step 2.

• NOT OK. - The signal frequency and 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 2. CHECK FOR AN OPEN IN THE SENSOR CIRCUIT AT BOTH OF THE ECM MODULES

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

2. Disconnect the machine harness connectors J3 and J1 from the left joystick. At the harness connectors for the joystick, place a jumper wire between the signal contact J3-1 (wire U741-OR(Orange)) and the ground 1 contact J1-3 (wire L731-BR(Brown)).

3. Disconnect machine harness connectors J1 and J2 from the Transmission/Chassis ECM.

4. At the harness connector for the Transmission/Chassis ECM, measure the resistance from return contact J1-21 (wire L731-BR(Brown)) to signal contact J2-34 (wire U741-OR(Orange)).

5. Observe the resistance measurement and wiggle the connector of the ECM and the connector of the sensor. Gently pull on the wires and wiggle the wires for both connectors.

6. At the harness connectors for the joystick, move the jumper from the ground 1 contact and connect the jumper to ground 4 contact J3-3 (wire 998-BR(Brown)). The other end of the jumper wire remains connected to the signal contact J3-1 (wire U741-OR(Orange)).

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

8. At the harness connectors for the Implement ECM, measure the resistance from return contact J1-21 (wire 998-BR(Brown)) to signal contact J2-34 (wire U741-OR(Orange)).

9. Observe the resistance measurement and wiggle the connector of the ECM and the connector of the sensor. Gently pull on the wires and wiggle the wires for both connectors.

Expected Result:

Both resistance measurements are less than 5Ω at all times during the manipulation of the wiring harness and connectors.

Results:

• OK. - Both of the resistance measurements are less than 5Ω. The sensor circuit is not open in either input circuit of the ECM. Proceed to Test Step 3.

• NOT OK. - The resistance measurement at one or both of the ECM modules is greater than 5 ohms. There is an open or a bad connection in one or both of the signal circuits.

  Repair: If both of the resistance measurements are not correct, there is an open connection or a bad connection on the sensor side of the splice of the machine harness for the signal wire U741-OR(Orange).

  Refer to the complete Electrical System Schematic of the machine. Check all of the connectors that are in the sensor signal circuit. Ensure that all connections are clean, that all connections are secure and that all connections are in good condition.

  If one of the measurements is correct and the other measurement is not correct, there is an open connection or a bad connection on the ECM side of the splice of the machine harness for the signal wire U741-OR(Orange).

  In either case, refer to the complete Electrical System Schematic of the machine. Check all of the connectors that are in the suspected section of the circuit for the sensor signal. Ensure that all 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

Test Step 3. 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 circuit.

3. Reconnect all harness connectors in order to 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. Check the status of the CID 1473 FMI 08.

Expected Result:

The CID 1473 FMI 08 is not active.

Results:

• OK. - The CID 1473 FMI 08 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 08 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 this diagnostic code may have failed.

  If both the Transmission/Chassis ECM and the Implement ECM have activated this diagnostic code, it is 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