26SI Series Alternator – MID 122 – CID 1250 – FMI 09

Conditions Which Generate This Code:

This code signals a lack of communication between the PL300 and the PL121. The lack of communication can be caused by the following actions:

  • “Sub-Module Flashing” of the PL121 with old software (prior to v3.0) on the PL300

  • A failure in the harness between the PL300 and the PL121

  • A failure of the hardware of the PL121 and the PL300

Note: In versions of software prior tov3.1, if the code clears following a power cycle, verify that the GPS Receiver is shown as “Functional”. If the status for the GPS Receiver is shown as “Not Present”, the lack of communication still exists.

Test Step 1. CHECK THE VERSION OF SOFTWARE ON THE PL300.

By using Caterpillar Electronic Technician (Cat ET), check the version of software on the PL300. Click “Service” and then click “Submodule Programming”.

Expected Result:

The version of software should be version 3.0 or a later version.

Results:

  • OK – The version of software is version 3.0 or a later version. Proceed to Test Step 2.

  • NOT OK – The version of software is not version 3.0 or a later version.

    Repair: Flash the PL300 with the latest version of software. The version of software should be version 3.0 or a later version. Clear the diagnostic code.

    STOP

Test Step 2. VERIFY POWER FROM THE PL300 TO THE PL121.

  1. Use a multimeter in order to verify power from the PL300 to the PL121.
  1. Disconnect the 12-pin connector from the PL121.
  1. Check the voltage on pin 1 and pin 2.

Expected Result:

The voltage should be between 11 VDC and 32 VDC.

Results:

  • OK – The voltage is 11 VDC to 32 VDC. Proceed to Test Step 3.

  • NOT OK – The voltage is not 11 VDC to 32 VDC.

    Repair: Check the harness for damage. Repair the harness or replace the harness. Clear the diagnostic code.

    STOP

Test Step 3. EXCHANGE THE PL121 WITH A “KNOWN GOOD UNIT”.

Replace the PL121 with a second PL121. Before replacing the Product Link, contact your Caterpillar Technical Communicator. Refer to Systems Operation, Troubleshooting, Testing and Adjusting, “Electronic Control Module (ECM) – Replace”.

Expected Result:

The diagnostic code should be cleared.

Results:

  • OK – The diagnostic code was cleared.

    Repair: The Product Link should be replaced. Before replacing the Product Link, contact your Caterpillar Technical Communicator. Refer to Systems Operation, Troubleshooting, Testing and Adjusting, “Electronic Control Module (ECM) – Replace”.

    STOP

  • NOT OK – The diagnostic code was not cleared. Proceed to Test Step 4.

Test Step 4. REPLACE THE PL300.

Replace the PL300.

Expected Result:

The diagnostic code should be cleared.

Results:

  • OK – The diagnostic code was cleared.

    Repair: Replace the PL300. Before replacing the Product Link, contact your Caterpillar Technical Communicator. Refer to Systems Operation, Troubleshooting, Testing and Adjusting, “Electronic Control Module (ECM) – Replace”.

    STOP

  • NOT OK – The diagnostic code was not cleared.

    Repair: Repeat the diagnostic procedure. If the diagnostic code still exists, contact your Caterpillar Technical Communicator for additional assistance.

    STOP

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