CB-634D Paving Compactor Machine Electronic Control System Reverse Propel Caterpillar


Reverse Propel
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System Operation Description:




Illustration 1g00949451

Note: When performing this procedure, the potentiometer for variable speed control needs to be turned fully clockwise. On machines equipped with this feature, this dial is on the instrument panel.

Test Step 1. DETERMINE THE PROBLEM.

The reverse propel function can fail in two ways. The machine may be stuck in reverse propel or the machine may not travel reverse.

Results:

  • STUCK IN REVERSE - The machine is stuck in the reverse mode. Proceed to Test Step 2.

  • NO REVERSE TRAVEL - The machine will not travel reverse. Proceed to Test Step 5.

Test Step 2. CHECK THE JOYSTICK POSITION SENSOR.

  1. At the back of the harness connector for the sensor, insert the probe of the 7X-1710 Multimeter Probe along the signal wire (contact 3).

  1. At the back of the harness connector for the sensor, insert the other 7X-1710 Multimeter Probe along the ground wire (contact 2).

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

  1. Monitor the duty cycle of the sensor with the 146-4080 Digital Multimeter .

  1. Move the joystick to the NEUTRAL position. Check the signal. The signal should be operating at a 50% duty cycle.

  1. Move the joystick slowly reverse. Check the signal.

Expected Result:

The value for the duty cycle starts at 50% in the center position and then the signal drops below 50% as the joystick is moved reverse.

Results:

  • OK - The value for the duty cycle starts at 50% in the center position and then the signal drops below 50% as the joystick is moved reverse. The joystick position sensor is operating normally. Proceed to Test Step 3.

  • NOT OK - The value for the duty cycle starts below 50% in the center position and then the signal remains below 50% as the joystick is moved reverse. The signal from the jostick is incorrect.

    Repair: Re-check the operation of the joystick and replace the joystick if the problem remains.

    Stop.

Test Step 3. CHECK THE CIRCUIT FROM THE ECM TO THE REVERSE PROPEL SOLENOID.

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

  1. At the ECM connector, remove the K726-BU wire from socket 37.

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

  1. Start the machine to check for reverse movement. Then, turn off the engine.

Expected Result:

The machine will not move reverse.

Results:

  • OK - The machine does not move reverse.

    Repair: The machine does not move after the wire is removed from the ECM. The ECM may be incorrectly sending a signal to the solenoid. The ECM may have failed. Exit this procedure and perform this entire procedure again. If the problem with the ECM remains, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM ) - Replace".

    Stop.

  • NOT OK - The machine moves reverse. The circuit from the ECM to the solenoid may be shorted to +battery. Proceed to Test Step 4

Test Step 4. CHECK THE SOLENOID CIRCUIT FOR A SHORT TO +BATTERY.

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

  1. At the wire that was removed from the ECM connector (K726-BU), measure the voltage from the wire to frame ground.

Expected Result:

No voltage is present.

Results:

  • OK - No voltage is present.

    Repair: No voltage is present but the machine still travels reverse when the engine is started. The solenoid may have failed. Replace the solenoid and resume normal machine operation. If a new solenoid does not solve the problem, check the pump.

    Stop.

  • NOT OK - Voltage is present.

    Repair: The wiring harness has failed. Repair the wiring harness or replace the wiring harness.

    Stop.

Test Step 5. CHECK THE BRAKES.

  1. Place the propel lever in the neutral position.

  1. Release the parking brake switch.

Expected Result:

The lamp for the brakes turns OFF.

Results:

  • YES - The lamp for the brakes turns OFF. The machine still does not move reverse. Proceed to Test Step 6.

  • NO - The lamp for the brakes remains ON.

    Repair: Troubleshoot the brake system. The brake system includes the following components: neutral start relay number 1, neutral start relay number 2, brake release latching relay, brake release relay and brake release solenoid. See the schematic at the beginning of this procedure.

    Stop.

Test Step 6. CHECK THE BRAKE SOLENOID.

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

  1. Ensure that the brake switch is in the OFF position.

  1. At the brake release solenoid, measure the voltage from contact 1 to contact 2.

Expected Result:

The voltage is approximately 12 DCV.

Results:

  • OK - The voltage is approximately 12 DCV. Proceed to Test Step 7.

  • NOT OK - The voltage is less than 12 DCV. There is a problem with the brake system.

    Repair: Troubleshoot the brake system. The brake system includes the following components: brake switch, neutral start relay number 1, neutral start relay number 2, brake release latching relay, brake release relay and brake release solenoid. See the schematic at the beginning of this procedure.

    Stop.

Test Step 7. CHECK THE JOYSTICK POSITION SENSOR.

  1. At the back of the harness connector for the ECM, insert the probe of the 7X-1710 Multimeter Probe along the signal wire (contact 15).

  1. At the back of the harness connector for the ECM, insert the other 7X-1710 Multimeter Probe along the ground wire (contact 2).

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

  1. Monitor the signal of the sensor with the 146-4080 Digital Multimeter .

  1. Move the joystick to the NEUTRAL position. Check the signal. The signal should be operating at a 50% duty cycle at 500 Hz.

  1. Move the joystick slowly reverse. Check the signal.

Expected Result:

The value for the duty cycle starts at 50% in the center position and then the signal drops below 50% as the joystick is moved reverse. The frequency is constant at 500 Hz.

Results:

  • OK - The value for the duty cycle starts at 50% in the center position and then the signal drops below 50% as the joystick is moved reverse. The frequency is 500 Hz. The joystick position sensor is operating normally. Proceed to Test Step 10.

  • NOT OK - The value for the duty cycle is incorrect or the frequency is not be 500 Hz. The signal from the jostick is incorrect. Proceed to Test Step 8.

Test Step 8. CHECK FOR POWER AND GROUND AT THE JOYSTICK.

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

  1. At the back of the harness connector for the joystick, insert the probe of the 7X-1710 Multimeter Probe along the power wire 137-BU (contact 1).

  1. At the back of the harness connector for the joystick, insert the probe of the 7X-1710 Multimeter Probe along the ground wire 200-BK (contact 2).

  1. Measure the voltage from contact 1 to contact 2.

Expected Result:

The voltage is approximately 12 volts.

Results:

  • OK - The voltage is approximately 12 volts. Proceed to Test Step 9.

  • NOT OK - No voltage is present. The wiring harness has failed.

    Repair: Repair the wiring harness or replace the wiring harness.

    Stop.

Test Step 9. CHECK THE JOYSTICK POSITION SENSOR.

  1. At the back of the harness connector for the joystick, insert the probe of the 7X-1710 Multimeter Probe along the signal wire (contact 3).

  1. At the back of the harness connector for the joystick, insert the other 7X-1710 Multimeter Probe along the ground wire (contact 2).

  1. Monitor the signal of the sensor with the 146-4080 Digital Multimeter .

  1. Move the joystick to the NEUTRAL position. Check the signal. The signal should be operating at a 50% duty cycle at 500 Hz.

  1. Move the joystick slowly reverse. Check the signal.

Expected Result:

The value for the duty cycle starts at 50% in the center position and then the signal drops below 50% as the joystick is moved reverse. The frequency is constant at 500 Hz.

Results:

  • OK - The value for the duty cycle starts at 50% in the center position and then the signal drops below 50% as the joystick is moved reverse. The frequency is 500 Hz. The joystick position sensor is operating normally.

    Repair: The signal wire is open between the joystick and the ECM. Repair the wiring harness or replace the wiring harness.

    Stop.

  • NOT OK - The value for the duty cycle is incorrect or the frequency is not be 500 Hz. The signal from the jostick is incorrect.

    Repair: The joystick may have failed. Recheck the joystick and replace the joystick if the problem remains.

    Stop.

Test Step 10. CHECK THE GROUND CIRCUIT AT THE SOLENOID.

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

  1. At the solenoid, measure the resistance from contact 4 to frame ground.

Expected Result:

The resistance is less than 5 ohms.

Results:

  • YES - The resistance is less than 5 ohms. The ground circuit is good. Proceed to Test Step 11.

  • NO - The resistance is over 5 ohms. The resistance is excessive.

    Repair: The ground circuit has failed. Repair the ground circuit.

    Stop.

Test Step 11. CHECK THE OUTPUT TO THE SOLENOID.

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

  1. At the back of the harness connector for the solenoid, remove the signal wire K726-BU.

  1. At the solenoid, connect one lead from the multimeter to contact 1. Connect the other lead from the multimeter to the removed wire K726-BU.

  1. Start the machine and move the propel lever to the reverse position.

  1. Measure the current.

Expected Result:

The current is 0 mA is neutral and rises to 1200 mA as the lever is moved reverse.

Results:

  • OK - The current is 0 mA in neutral and rises to 1200 mA as the lever is moved reverse. The proper current is reaching the solenoid. Proceed to Test Step 13.

  • NOT OK - The current is 0 mA is neutral and does not rise as the lever is moved reverse. The proper signal is not reaching the solenoid. Proceed to Test Step 12.

Test Step 12. CHECK FOR AN OPEN CIRCUIT.

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

  1. Remove the machine harness from the ECM.

  1. At the harness connector for the ECM, connect one lead from the multimeter contact 37 (wire K726-BU).

  1. At the propel control solenoid, disconnect the 4 pin connector and connect the other lead from the multimeter to wire K726-BU.

  1. Measure the resistance of wire K726-BU.

Expected Result:

The resistance is less than 5 ohms.

Results:

  • OK - The resistance is less than 5 ohms. The circuit is not open. The ECM is not sending the proper signal to the solenoid.

    Repair: The ECM may have failed. Ensure that the brake circuit is correct and the signal for brake release is reaching the ECM. If the problem remains, contact the Technical Communicator at the dealership for possible consultation with AVSpare. This consultation may greatly reduce repair time.

    Stop.

  • NOT OK - The resistance is over 5000 ohms. The circuit is open between the ECM and the solenoid.

    Repair: Repair the wiring harness or replace the wiring harness.

    Stop.

Test Step 13. CHECK THE COIL OF THE SOLENOID.

At the solenoid, measure the resistance between contact 1 and contact 2.

Expected Result:

The resistance is 10 ohms.

Results:

  • OK - The resistance is 10 ohms. The coil of the solenoid is OK.

    Repair: The electronic portion of the reverse propel function is not the source of the problem. Exit this procedure and perform this procedure again. If the cause of the problem is not found, check the hydraulics and the propel motor.

    Stop.

  • NOT OK - The resistance is not 10 ohms.

    Repair: The solenoid has failed. Replace the solenoid.

    Stop.

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