D6N Track-Type Tractor Caterpillar

Illustration 1	g02623967
Connections of the service brake pedal position sensor

A CID 0468 is associated with the service brake pedal position sensor. An FMI 08 means the ECM has determined that the signal from the pedal position sensor has an abnormal pulse width, frequency, or period.

Note: The service brake pedal position sensor is a PWM sensor. The position sensor is a PWM sensor that operates at a frequency of 500 ± 100 hz. The optimal frequency is approximately 500 hz. The sensor sends a PWM input signal to the Power Train ECM that indicates the pedal position. The voltage of the signal ranges from 0 to 5 VDC. The ECM recognizes a valid duty cycle of 5 percent (0.25 VDC) to 95 percent (4.75 VDC). The duty cycle of the sensor signal increases as the pedal is depressed. The operating range of the sensor, when mounted to a pedal assembly, may not equal the full 5% to 95% duty cycle range of the sensor.

The possible causes for this diagnostic code are listed:

• Sensor failure.

• Sensor open or intermittent connection to +battery.

• Sensor circuit open or intermittent connections.

• Machine ECM failure, but is most unlikely.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear these diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 0468 FMI 08 is active before performing this procedure.

Use a digital multimeter for the measurements in the procedure.

System Response:

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

Test Step 1. CHECK THE SENSOR.

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

2. Disconnect the harness connector from the sensor.

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

4. Observe the status of the CID 0468 FMI 08 diagnostic code,

Expected Result:

The diagnostic code remains active.

Results:

• YES - The diagnostic code remains active. The sensor is not causing the problem. Goto test step 2.

• NO - The diagnostic code does not remain active. The sensor has failed.

  Repair: Replace the sensor.

  Go to Test Step 4.

Test Step 2. CHECK THE HARNESS FOR AN OPEN CIRCUIT.

1. The sensor remains disconnected from the harness.

2. Turn the disconnect switch, and the start switch, to the OFF position.

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

4. At the sensor harness connector, insert a jumper wire from the contact for wire F790-BR to the contact for wire J766-PU.

5. At the J1 and J2 ECM harness connectors, measure resistance from J2-32 (wire F790-BR) to contact J1-45 (wire J766-PU).

6. At the sensor harness connector, reset the jumper wire. This time, from the contact for wire F790-BR to the contact for wire 497-BU.

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

Expected Result:

Each resistance is less than 5 ohms.

Results:

• YES - Each resistance is less than 5 ohms. There are no open sensor circuits in the harness. Goto Test Step 3.

• NO - A resistance is greater than (+/-) 5000 ohms. There is an open sensor circuit in the harness.

  Repair: Repair or replace the harness.

  Go to Test Step 4.

Test Step 3. CHECK THE HARNESS FOR A SHORT CIRCUIT.

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

2. The J1 and J2 ECM harness connectors remain disconnected.

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

Expected Result:

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

Results:

• YES - Each resistance is more than (+/-) 5000 ohms. There are no shorted sensor circuits in the harness. Go to Test Step 4.

• NO - A resistance is less than 5000 ohms. There is a shorted sensor circuit in the harness.

  Repair: The short is from contact J2-3 (wire G730-PK) to the circuit with the low resistance measurement. Repair or replace the harness.

  Go to Test Step 4.

Test Step 4. CHECK THE DIAGNOSTIC CODE STATUS.

1. Inspect and clean all contacts in the harness connectors. Reconnect all harnesses. Make sure all the connectors are securely tightened.

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

3. Clear all inactive diagnostic codes.

4. Operate the machine.

5. Observe the status of the CID 0468 FMI 08 diagnostic code.

Expected Result:

The diagnostic code is no longer active.

Results:

• YES - The diagnostic code is no longer active, and does not exist at this time. The problem has been corrected.

  Repair: Return machine to normal operation

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• NO - The diagnostic code is still active. The cause for the problem has not been corrected.

  Repair: If you have not inspected the harness connectors in a previous Test Step, do that now. Clean the contacts of the harness connectors. Check the wires for damage to the insulation caused by excessive heat, battery acid, or chafing.Perform a 45 N (10 lb.) pull test on each of the wires that are associated with the sensor circuit.Perform a "wiggle test" on the sensor circuit of the machine wiring harness, using the Caterpillar Electronic Technician service tool. The "wiggle test" can be used to detect open or shorted connections in the machine wiring harness.Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are securely fastened. Perform Test Step 4 again. If the problem has NOT been found, and the original code is still active, the machine ECM may have failed.Prior to replacing an ECM, always contact your Dealership Technical Communicator for possible consultation with Caterpillar, or with the Dealer Solutions Network. This consultation may greatly reduce repair time. If the ECM needs to be replaced, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP