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| Illustration 1 | g02623967 |
Connection of the service brake pedal position sensor | |
This diagnostic code is recorded when the ECM determines that the voltage is below normal.
The sensor is a PWM sensor that operates at approximately 500 Hz. The sensor operating duty cycle is from 5% to 95%. The sensor operating duty cycle range, when mounted to a pedal assembly, may not equal a full 5% to 95% operating range. The duty cycle should increase as the pedal is pressed.
The possible causes for this diagnostic code are listed:
- The sensor has failed.
- The sensor output signal shorted to ground.
- Intermittent connections or poor connections
- Mechanical devices are loose.
- 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 FOR POWER AT THE SENSOR.
- Do not disconnect the harness connector from the sensor.
- At the back of the harness connector for the sensor, insert a multimeter probe along contact A (wire 497-BU) for the voltage supply. Insert another multimeter probe along contactB B (wire J766-PU).
- Turn the key start switch and the disconnect switch to the ON position.
- Measure the voltage from contact A (wire 497-BU) to contact B (wire J766-PU).
Expected Result:
The voltage is 8 DCV.
Results:
- OK - The voltage is 8 DCV. Proceed to Test Step 2.
- NOT OK - The voltage is not 8 DCV. The circuit is open.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 2. CHECK THE SIGNAL CIRCUIT OF THE SENSOR.
- Turn the key start switch and the disconnect switch to the OFF position.
- At the back of the harness connector for the sensor, remove the multimeter probe from contact A and insert the probe along contact C.
- At the back of the harness connector for the sensor, insert the multimeter probe along contact B.
- Turn the disconnect switch and the key start switch to the ON position.
- Monitor the signal of the sensor with the digital multimeter.
- Without disconnecting the sensor or the associated hardware from the machine, take the sensor through the full operating range.
Expected Result:
The sensors signal responds in the manner that is described at the beginning of this procedure.
Results:
- OK - The sensors signal responds correctly. The sensor is operating correctly. Proceed to Test Step 3.
- NOT OK - The sensors signal does not respond correctly. The sensor is NOT operating correctly.
Repair: Replace the sensor.
STOP
Test Step 3. CHECK THE SIGNAL CIRCUIT AT THE ECM.
- Turn the key start switch and the disconnect switch to the OFF position.
- Insert the multimeter probe into the back of the ECM connector along J2-32 (wire F790-BR) and J1-45 (wire J766-PU).
- Turn the disconnect switch and the key start switch to the ON position.
- Monitor the signal of the sensor with the digital multimeter.
- Without disconnecting the sensor or the hardware associated with the sensor from the machine, take the sensor through the full operating range.
Expected Result:
The sensors signal responds in the manner that is described at the beginning of this procedure.
Results:
- OK - The sensors signal responds correctly. The sensor is operating correctly. Proceed to Test Step 4.
- NOT OK - The sensors signal does not respond correctly. The harness has failed.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 4. CHECK THE SIGNAL CIRCUIT FOR A SHORT IN THE HARNESS.
- The key start switch and the disconnect switch remain in the OFF position.
- Disconnect the machine harness connectors from the sensor and the ECM.
- Measure the resistance between contact J2-32 (wire F790-BR) and all contacts that are used in the machine harness connectors for the ECM.
Expected Result:
The resistance is greater than 5000 ohms.
Results:
- OK - The resistance is greater than 5000 ohms. The circuit is correct. Proceed to Test Step 5.
- NOT OK - The resistance is less than 5 ohms. The signal circuit is shorted to another circuit in the harness.
Repair: There is a short in the machine harness. Repair the circuit with the low resistance measurement.
STOP
Test Step 5. CHECK THE STATUS OF THE DIAGNOSTIC CODE
- Inspect the harness connectors. Clean the contacts of the harness connectors and 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 circuit.
- 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.
- Turn the disconnect switch and the key start switch to the ON position.
- Operate the machine.
- 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. If the Caterpillar Electronic Technician (Cat ET) is available, use the 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