D6N Track-Type Tractor Caterpillar

Illustration 1	g02623967
Connections of the service brake pedal position sensor

This diagnostic code is associated with the service brake pedal position sensor. The FMI 03 means that the Machine ECM determined that the voltage is above normal.

The possible causes of this diagnostic code are listed:

• The supply circuit to the sensor is open.

• The return circuit is open.

• The signal circuit is shorted to the +battery.

• The signal circuit is open or the sensor is disconnected.

• The sensor has failed.

• The ECM has failed. An ECM failure is unlikely.

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. Ensure that the diagnostic code of CID 0468 FMI 03 is active before performing this procedure.

Note: Use a digital multimeter for the measurements in this procedure.

System Response:

A level 2 warning will be generated. The action lamp will be ON and flashing.

Test Step 1. CHECK THE DUTY CYCLE OF THE SENSOR SIGNAL

1. Turn the keyswitch and the disconnect switch to the ON position. Do not start the engine.

2. Use a multimeter capable of measuring a duty cycle to check the duty cycle value of the position sensor. At the connected ECM connectors, insert a multimeter probe in the back of signal contact J2-32 (wire F790-BR) and contact J1-45 (wire J766-PU).

3. Take the sensor through the full range of motion.

Expected Result:

The sensor duty cycle should be in the range of 5% to 95%. The duty cycle should increase as the pedal is pressed to the floor. Sensor operating range, when mounted to a pedal assembly, may not equal the full 5% to 95% sensor duty cycle.

Results:

• OK - The duty cycle values are in the correct range. The operation of the sensor is correct. Proceed to Test Step 5.

• NOT OK - The duty cycle values are not in the correct range. Proceed to Test Step 2.

Test Step 2. CHECK THE VOLTAGE AT THE SENSOR

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

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

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

4. At the machine harness connector for the sensor, measure the voltage between contact A (wire 497-BU) and contact B (wire J766-PU).

Expected Result:

The voltage is approximately 8 VDC.

Results:

• OK - The voltage is approximately 8 VDC. Proceed to Test Step 3.

• NOT OK - The voltage measurement is NOT 8 VDC.

  Repair: There may be an open in the machine harness. Check the fuse for the circuit. Ensure that the fuse is not open. If the fuse is open, replace the fuse. Clear all of the diagnostic codes. Check if the diagnostic code is still active. If the code is still active, perform this step again. If supply voltage is not present at the sensor connector, there is an open in the supply circuit of the machine harness. Repair the machine harness or replace the machine harness.

  STOP

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

Note: The connector for the sensor should remain disconnected from the machine harness.

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

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

3. At the ECM harness connectors, measure resistance from contact J2-32 (wire F790-BR) to contact J1-44 (wire 497-BU).

Expected Result:

Resistance is less than 5 ohms.

Results:

• OK - Resistance is less than 5 ohms. Proceed to Test Step 5.

• NOT OK - Resistance is greater than 5 ohms. There is an open or a bad connection in the sensor circuit in the harness.

  Repair: Refer to the complete electrical schematic in the service manual. Check all of the harness connectors that are in the circuit for bad connections. Repair or replace the harness.

  STOP

Test Step 4. CHECK THE SIGNAL CIRCUIT FOR A SHORT

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

2. The sensor remains disconnected from the harness.

3. The J1 and J2 harness connectors remain disconnected from the ECM.

4. At the J1 machine harness connector for the ECM, measure resistance from contact J2-32 (wire F790-BR) to all other J1 and J2 contacts used in both the J1 and J2 ECM harness connectors.

Expected Result:

Each resistance measurement more than (+/-) 5000 ohms.

Results:

• OK - Each resistance measurement more than (+/-) 5000 ohms.

  Repair: The sensor has failed. Replace the sensor. Calibrate the sensor if necessary. Refer to Testing and Adjusting Calibration, UENR0057. Verify that the new sensor corrected the problem.

  STOP

• NOT OK - A resistance measures less than 5 ohms.

  Repair: There is a short in the machine harness. The short is between wire F790-BR and the wire with the low resistance. Repair or replace the harness.

  STOP

Test Step 5. CHECK THE STATUS OF THE DIAGNOSTIC CODE

1. Inspect the harness connectors. Clean the contacts of the harness connectors and check the wires for damage to the insulation that is caused by excessive heat, corrosion, 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. Also, make sure that the clips for each connector are 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 diagnostic code.

Expected Result:

The diagnostic code is active.

Results:

• YES - The diagnostic code is active. The diagnostic code has not been corrected.

  Repair: Check the circuit again. Use the Caterpillar Electronic Technician (Cat ET) service tool in order to perform a "Wiggle Test" on the machine wiring harness. The "Wiggle Test" can detect shorts and opens in the machine wiring harness that are momentary or intermittent.An ECM failure is unlikely. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. Prior to replacing an ECM, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Troubleshooting, "Electronic Control Module (ECM) - Replace".

  STOP

• NO - The diagnostic code is not active. The initial diagnostic code was probably caused by a poor electrical connection at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation.STOP