26SI Series Alternator – Electronic Service Tool Does Not Communicate with ECM

System Operation Description:

During the installation of a Product Link 321 system, the wiring harness is connected to the existing Cat Data Link wiring on the machine. If this is not done properly, the continuity of the Cat Data Link wiring may be open intermittently. This condition may not be apparent immediately. This will cause a problem when you are trying to connect the Caterpillar Electronic Technician (Cat ET service tool) to the machine.

  • Cat ET may report that no ECM has been found.

  • Cat ET may not report every ECM that is on the machine.

  • Cat ET may report an ECM but the ECM will not have any data.

If the wires for the Cat Data Link are reversed during the installation, the Product Link ECM will not be shown after connecting Cat ET to the machine.

Test Step 1. VERIFY THAT THE CAT DATA LINK WIRES ARE NOT REVERSED.

  1. Check that the positive Cat Data Link (CDL+) wire (893-GN) in the wiring harness for the Product Link is connected to the CDL+ wire (893-GN or 944-OR) of the wire harness for the machine.
  1. Check that the negative Cat Data Link (CDL-) wire (892-BR) in the wiring harness for the Product Link is connected to the negative Cat Data Link (CDL-) wire (892-BR or 945-BR) of the wire harness for the machine.

Expected Result:

The Cat Data Link wires are properly connected.

Results:

  • OK – The wires for the Cat Data Link are properly connected. Proceed to Test Step 2.

  • NOT OK – The wires for the Cat Data Link are reversed.

    Repair: Reinstall the Cat Data Link wires correctly and check the operation of the Product Link module by using Cat ET.

    STOP

Test Step 2. CHECK THE WIRING WITH A MULTIMETER.

  1. Turn off the machine and turn the disconnect switch to the OPEN position.
  1. Measure the resistance of the negative Cat Data Link wire from the service connector (contact “E”) to the location for the spliced Cat Data Link wire. Note the resistance.
  1. Measure the resistance of the positive Cat Data Link wire from the service connector (contact “D”) to the location for the spliced Cat Data Link wire. Note the resistance.

Expected Result:

The resistance in both wires is less than 5 ohms.

Results:

  • OK – The resistance is less than 5 ohms. Proceed to Test Step 3.

  • NOT OK – The resistance is greater than 5 ohms. Repair the wiring harness.

    Repair: After repairing, resume the setup procedures for the installation of the Product Link.

    STOP

Test Step 3. VERIFY THAT THE WIRING FOR THE CAT Data Link IS PROPERLY CONNECTED.

  1. Check the spliced connections for the Cat Data Link that were made during the installation. Verify that all connections are clean and tight.
  1. Reconnect the harness connectors that were disturbed during the installation. Ensure that all of the pins are correctly seated in the sockets.
  1. Reconnect the cable from the service tool connector. Attempt to access the Cat Data Link by using Cat ET.

Expected Result:

Cat ET lists the ECM systems that are available on the machine. The ECM for the Product Link can be accessed.

Results:

  • OK – Cat ET lists the electronic control modules that are available on the machine. The ECM for the Product Link can be accessed. Resume the setup procedures for the installation of the Product Link.STOP

  • NOT OK – The Cat ET does not list the electronic control modules that are available on the machine. The ECM for the Product Link cannot be accessed. Proceed to Test Step 4.

Test Step 4. CHECK FOR A MONITORING SYSTEM.

Check if the machine is equipped with a monitoring system. Some common monitoring systems include the following systems: Electronic Monitoring System, Computerized Monitoring System, Caterpillar Monitoring System, VIDS and VIMS. Also, many machines have monitors that are specific to the type of machine such as excavators and cold planers.

Expected Result:

The machine is equipped with a monitor.

Results:

  • YES – The machine is equipped with a monitoring system. Proceed to Test Step 5.

  • NO – The machine is not equipped with a monitoring system. Proceed to Test Step 6.

Test Step 5. CHECK FOR A DIAGNOSTIC CODE FOR THE CAT Data Link.

Check the monitoring system for a diagnostic code for the Cat Data Link.

Expected Result:

There is a diagnostic code for the Cat Data Link.

Results:

  • YES – There is a diagnostic code for the Cat Data Link .

    Repair: Perform the troubleshooting procedure for that diagnostic code that is found in the service manual for that ECM.

    STOP

  • NO – There are no diagnostic codes for the Cat Data Link. Proceed to Test Step 6.

Test Step 6. RETURN THE WIRING TO THE ORIGINAL CONDITION.

  1. Return the Cat Data Link wires to the original condition. Remove any splices that were made and reconnect the wiring harness.
  1. Connect Cat ET to the service connector. Verify that all of the appropriate electronic control modules are present. The ECM for the Product Link will not be present.

Expected Result:

All of the appropriate electronic control modules are present.

Results:

  • YES – All of the appropriate electronic control modules are present. The wiring is correct at this time. Return to the installation procedure for the Product Link and reinstall the wiring for the Cat Data Link. Continue with the setup of the Product Link.STOP

  • NO – All of the appropriate electronic control modules are not present.

    Repair: A problem still exists with the Cat Data Link wiring. This problem does not relate to the installation of the Product Link. Troubleshoot the entire Cat Data Link circuit to all available electronic control modules. After the problem is found and the problem is corrected, return to the installation procedure for the Product Link. Reinstall the wiring for the Cat Data Link. Continue with the setup of the Product Link.

    STOP

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