D6N Track-Type Tractor Caterpillar

Illustration 1	g02729796
Direction Selector (FNR) Switch connections.

The CID 3527 diagnostic code is associated with the Direction Selector Rocker Switch (FNR switch).

The Direction Selector switch is a three position rocker switch is located on the Speed / Direction Handle. The switch contains two hall effect position sensors. These sensors provide two PWM input signals to the Machine ECM which will indicate the position of the rocker switch.

The two switch position sensors are the Direction Selector Position Sensor 1 (FNR sensor 1) and the Direction Selector Position Sensor 2 (FNR sensor 2)

The FMI 12 means that the ECM has detected the PWM duty cycle signals are being received from both position sensors are not in the acceptable range.

The conditions that can cause the Machine ECM to activate this diagnostic code are listed:

• The Direction Selector switch has failed.

• The ECM power supplies for both of the position sensors have been interrupted.

• Both of the sensor signal circuits have a problem in the machine harness.

• The ECM has failed. This failure is unlikely.

The Machine ECM monitors the two switch input circuits in order to determine the status of the FNR three-position rocker switch. Each of the two internal hall effect sensors in the switch send a PWM duty cycle signal to the ECM on each of the input circuits. The ECM expects that the duty cycle from both of the sensors to be approximately the same at any given position. The duty cycle ranges for each switch position that the ECM will consider acceptable are illustrated in the following Table.

The FNR Sensor 1 receives power and ground from the Machine ECM 10 V power supply. The FNR Sensor2 receives power and ground from the Machine ECM 8 V power supply.

Note: If a diagnostic code is active for either the ECM 10 V power supply (CID 1482) or the ECM 8 V power supply (CID 0041), fix the power supply problem before performing this procedure.

Note: The following test procedure may cause other diagnostic codes to be activated. Ignore these created diagnostic codes and clear the diagnostic codes when the problem has been corrected. Ensure that the CID 3527 FMI 12 diagnostic code is active before performing this procedure.

Test Step 1. CHECK THE SENSOR POWER SUPPLY

1. Turn the disconnect switch and the key switch to the ON position. Do not start the Engine.

2. At the harness connector for the FNR switch, use 7X-1710 Multimeter Probes to check the following circuit voltages:
   • The FNR sensor 1 10 V power supply between contact 9 (wire 709-OR) and contact 10 (wire J765-BU). The voltage should be 10.0 ± 0.5 V.

   • The FNR sensor 2 8 V power supply between contact 11 (wire 497-BU) and contact 12 (wire J766-PU). The voltage should be 8.0 ± 0.4 V.

3. At the harness connector for the FNR switch, use 7X-1710 Multimeter Probes to check the following sensor circuit PWM duty cycles at each switch position:
   • The FNR sensor 1 signal circuit between contact 7 (wire E946-OR) and contact 10 (wire J765-BU). Refer to Table 1.

   • The FNR sensor 2 signal circuit between contact 8 (wire E947-WH) and contact 12 (wire J766-PU). Refer to Table 1.

Expected Result:

The voltage measurements for the ECM power supplies are correct. The PWM duty cycle measurements for both of the position sensor circuits are not in the acceptable ranges at each switch position according to the table at the beginning of this procedure.

Results:

• YES - The power supply circuits are correct. The duty cycles of both of the sensors are not correct. The most likely cause is that the switch has failed, however, proceed to Test Step 2 in order to check the switch with the machine harness disconnected.

• NO - Both of the ECM power supplies are not correct. The sensor power supplies could be causing the problem.

  Repair: Check for and resolve any active diagnostic code for the ECM 10 V power supply and the ECM 8 V power supply. Verify that the return circuits are not causing the problem.If power supply diagnostic codes are not active, a harness connector is likely disconnected or damaged.Refer to the complete machine Electrical System Schematic. Check all of the connectors that are in the power supply circuits. Ensure that all connections are clean, secure and in good condition. Repair the machine harness or replace the machine harness.Refer to the Machine, CID 0041 diagnostic code procedure and the Machine, CID 1482 diagnostic code procedure in order to troubleshoot the Machine ECM power supplies.

  STOP

• NO - Both of the ECM power supplies are correct and both of the sensor duty cycles are in the acceptable ranges at each of the switch positions. The measurements are indicating that the selector switch is operating properly. Proceed to Test Step 3.

Test Step 2. CHECK THE SWITCH

Note: This step will check the switch signal while isolated from the machine harness.

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

2. At the 12 contact harness connector for the FNR Switch, use a 151-6320 Removal Tool or a similar tool to remove the FNR 1 signal circuit at contact 7 ( wire E946-OR) and the FNR 2 signal circuit at contact 8 (wire E947-WH) from the harness connector. The harness connector will remain connected to the handle connector.

3. At the FNR switch 12 contact connector, insert the negative side 7X-1710 Multimeter Probe along the sensor return contact 12 (wire J766-PU). Use the positive multimeter probe to contact the FNR sensor 1 signal pin at contact 7 by either inserting the probe in the back of the switch connector at contact 7 or by inserting the probe through the harness connector where the signal wire was removed. Ensure that good contact is made with the sensor signal pin.

4. Turn ON the key switch. While observing the duty cycle percentage, move the FNR rocker switch to each of the three switch positions.

5. Repeat step "C" and step "D" at contact 8 in order to check the duty cycle of the FNR sensor 2 signal.

Expected Result:

Refer to Table 1 at the beginning of this procedure. The PWM duty cycle signals for each of the sensor input signals should be in the acceptable range that is listed for each switch position.

Results:

• OK - Both of the switch input signal PWM duty cycle signals are correct according to the table at the beginning of this procedure. The measurements are not indicating that the FNR switch is causing the problem.
  Reinstall the signal wires and sockets that were removed back in the original location at in the machine harness connector for the FNR Switch. Verify that all of the FNR Switch wires are in the correct locations and secure in the connector before proceeding to the next step.
  
  Proceed to Test Step 4.

• NOT OK - Both of the switch PWM duty cycle signals are not correct according to the table at the beginning of this procedure. The FNR Switch operation is not correct.

  Repair: Repeat this test step in order to verify that the FNR sensor operation is not correct. If the same result is observed, replace the FNR Switch.The FNR switch is serviceable. If the switch operation is not correct, replace the FNR Switch.After the FNR Switch is replaced, verify that the new switch is operating correctly before operating the machine.

  STOP

Test Step 3. CHECK THE SWITCH SIGNAL CIRCUITS FOR AN OPEN

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

2. Disconnect the 12 contact harness connector from the FNR Switch connector.

3. At the machine harness connector for the switch, connect a jumper wire between the FNR sensor 1 signal contact 1 (wire E946-OR) and the FNR sensor 2 signal contact 8 (wire E947-WH).

4. Disconnect the machine harness connector J2 from the Machine ECM.

5. At the ECM harness connectors J2, measure the resistance between the FNR sensor 1 signal contact J2-48 (wire E946-OR) and the FNR sensor 2 signal contact J2-49 (wire E947-WH).

6. While observing the resistance measurement of the circuits, gently wiggle the machine harness near the ECM connectors and near the switch connector. Do not disconnect the jumper wire.

Expected Result:

The resistance measurement is less than 5 ohms at all times during the manipulation of the machine harness.

Results:

• OK - The resistance measurement is less than 5 ohms at all times during the manipulation of the machine harness. The resistance measurement is indicating that there is not an open or a poor connection in the switch circuits. Proceed to Test Step 4.

• NOT OK - The resistance measurement is greater than 5 ohms during the movement of the machine harness. There is an open or a poor connection in both of the signal circuits.

  Repair: A resistance measurement that is greater than 5000 ohms could indicate that a wire is either not connected or 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 open but is not in good connection.Both of the sensor circuits would have to be open in order fir this diagnostic code to be activated.Refer to the complete machine Electrical System Schematic. Check all of the connectors that are in the suspect sensor circuit. Ensure that all connections are clean, secure and in good condition. Repair the machine harness or replace the machine harness.

  STOP

Test Step 4. CHECK THE SWITCH SIGNAL CIRCUITS FOR A SHORT

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

The 12 contact harness connector remains disconnected from the FNR Switch connector.

1. The jumper wire that was connected in the last test step remains connected.

2. If not already disconnected, disconnect the harness connectors J1 and J2 from the Machine ECM.

3. At the Machine ECM harness connector J2, measure the resistance between the FNR sensor 2 circuit at contact J2-49 (wire E947-WH) and frame ground. Measure the resistance between the signal circuit at contact J2-49 and each of the other individual contacts that are used on the J1 and J2 connectors for the Machine ECM except for the FNR sensor 1 circuit J2-48.

Expected Result:

Each of the resistance measurements is greater than 5000 ohms.

Results:

• OK - Each resistance measurement is greater than 5000 ohms. The resistance measurements are not indicating that either of the sensor signal circuits are shorted to ground or to another circuit in the machine harness. Proceed to Test Step 5.

• NOT OK - One or more of the resistance measurements is less than 5000 ohms. There is a short in the machine harness.

  Repair: The FNR sensor signal circuits are shorted to either frame ground or to the circuit with the low resistance measurement in the machine harness.Refer to the complete machine Electrical System Schematic. Examine all of the connectors in the circuits for points in the machine harness where both circuits may be shorted to ground or to other circuits.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 and clean the contacts of the harness connectors that are in the affected circuit. Check the wires for damage to the insulation that can be caused by excessive heat or chafing.

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

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

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

5. Determine if the CID 3527 FMI 12 diagnostic code is active.

Expected Result:

The CID 3527 FMI 12 diagnostic code is not active.

Results:

• OK - The CID 3527 FMI 12 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 3527 FMI 12 diagnostic code is active. The problem has not been corrected.

  Repair: If the problem has not been corrected, use the Caterpillar Electronic Technician (Cat ET) service tool, if available, in order to perform a "Wiggle Test" on the sensor circuit in the machine wiring harness. The wiggle test can detect momentary or intermittent shorts or opens in the machine wiring harness.If the cause of the problem is not found, perform this procedure again. If all possible causes of the problem have been investigated and no problem can be found, the ECM may be activating the diagnostic code in error.Prior to replacing an ECM, always contact the Cat dealer Solutions Network (DSN) for consultation with company personnel. If the ECM must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP