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C13 and C15 On-highway Engines Caterpillar


Data Link - Test

Usage:

C15 B5R
System Operation Description:

This procedure verifies the integrity of the ATA data link and the J1939 data link between the following components:

  • Engine Control Module (ECM)

  • Service tool connector

If the Caterpillar Electronic Technician (ET) will not communicate with the ECM, refer to Troubleshooting, "Electronic Service Tool Does Not Communicate" before you begin this procedure. The procedure verifies that electrical power is being supplied to the ECM and to the service tool connector.

Background Information

The data links do not require a configuration parameter to be set to a particular value in order to be activated. The data links perform the following functions:

Communication Between Cat ET and the ECM - Cat ET communicates with the ECM via the data links.

Electronic Dashboard - Some electronic dashboards receive information via the data links. Refer to the vehicle service literature in order to determine if the vehicle dashboard is connected to a data link.

The engine ECM is connected to the service tool connector in the cab via wiring that is provided by the Original Equipment Manufacturer (OEM). The service tool connector contains connections for electrical power and for the data links.

When the keyswitch is in the OFF position, Cat ET may communicate with the ECM. However, the communications may be disrupted and the communications may require frequent reconnection. In order to avoid this problem, place the keyswitch in the ON position when Cat ET is being used.

Cat ET may display the following error message:

"The version of the ECM is not recognized and the integrity of the changed parameters and displayed data is not guaranteed."

This message indicates that one of the following conditions exist:

  • The flash file in the ECM is newer than the version of Cat ET.

  • The latest version of Cat ET has not been installed.

Show/hide table

Illustration 1g01273205

Information for the circuits for the round service tool connectors

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Illustration 2g01273226

Information for the circuits for the OBD II service tool connector

Test Step 1. Inspect Electrical Connectors and Wiring

    Note: Carefully following this procedure is a good way to identify an intermittent problem.

  1. Perform a visual inspection of the wiring between the P1 connector and the service tool connector. Look for these problems:

    • Harness damage that is caused by chafing

    • Harness damage that is caused by excessive heat

  1. Inspect the service tool connector:

    1. Look for moisture on the wiring and on the connector.
      Show/hide table

      Illustration 3g01273259

      Harness side of the service tool connectors

    1. Pull on the wires that are associated with the data links. Pulling verifies that the wire is properly attached to the terminal and that the terminal is properly inserted into the connector.

  1. Inspect the P1 connector:

    1. Look for moisture on the wiring and on the connector.
      Show/hide table

      Illustration 4g01273266

      Harness side of the P1 connector

    1. Pull on the wires that are associated with the data links. Pulling verifies that the wire is properly crimped to the terminal and that the terminal is properly inserted into the connector.

Expected Result:

All connectors, pins, and sockets are coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion or of pinch points.

Results:

  • OK - The wiring and the connectors appear to be OK. Proceed to Test Step 2.

  • Not OK - There is a problem with the wiring or with a connector.

    Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. Verify that the problem is resolved.

    STOP

Test Step 2. Bypass the Wiring for the Data Link

  1. Connect the 167-9225 Harness (SERVICE TOOL ADAPTER) to the J1 connector, to the 207-6845 Adapter Cable As , and to the vehicle battery.

  1. Try to establish communication between Cat ET and the ECM.

Expected Result:

Cat ET and the ECM communicate.

Results:

  • Yes - Cat ET and the ECM communicate when the bypass harness is installed. However, communication cannot be established via the vehicle wiring.

    Repair: If either data link is connected to the vehicle dashboard, disconnect the dashboard electrical connector that contains the wiring for the data link. Try to establish communication between Cat ET and the ECM.The problem is in the dashboard if disconnecting the dashboard allows Cat ET and the ECM to communicate. Refer to the original equipment manufacturer for assistance in repairing the problem.The dashboard is OK if the problem remains and the dashboard is disconnected. Proceed to the next Test Step.

    If either data link is not connected to the vehicle dashboard, proceed to Test Step 3.

  • No - Communication between Cat ET and the ECM is not established when the bypass harness is installed.

    Repair: Temporarily connect a test ECM. Refer to Troubleshooting, "Test ECM Mode". Verify that the problem is resolved.Connect the original ECM and verify that the problem returns. Replace the original ECM.

    STOP

Test Step 3. Check the Wiring for the Data Links for a Short Circuit

  1. Turn the keyswitch OFF.

  1. Disconnect both the positive cable and the negative cable from the vehicle battery in order to avoid false readings.

  1. Disconnect the P1 connector.

  1. Measure the resistance between the following terminals:

    • P1-8 (ATA Data Link +) and P1-63 (-Battery)

    • P1-9 (ATA Data Link -) and P1-63 (-Battery)

    • P1-50 (J1939 Data Link +) and P1-63 (-Battery)

    • P1-34 (J1939 Data Link -) and P1-63 (-Battery)

  1. Measure the resistance between the following terminals:

    • P1-8 (ATA Data Link +) and P1-52 (+Battery)

    • P1-9 (ATA Data Link -) and P1-52 (+Battery)

    • P1-50 (J1939 Data Link +) and P1-52 (+Battery)

    • P1-34 (J1939 Data Link -) and P1-52 (+Battery)

Expected Result:

Each measurement indicates an open circuit.

Results:

  • Yes - Each measurement indicates an open circuit. The wiring for the data links does not have a short circuit. Proceed to Test Step 4.

  • No - At least one measurement is less than five Ohms. The wiring for a data link has a short circuit.

    Repair: Determine the cause of the short circuit. Repair the problem, when possible. Replace parts, if necessary. Verify that the problem is resolved.

    STOP

Test Step 4. Check the Wiring for the Data Links for an Open Circuit

  1. Connect a jumper wire between terminals P1-8 and P1-9.

  1. At the service tool connector, measure the resistance between the terminals for the ATA data link.

  1. Connect a jumper wire between terminals P1-34 and P1-50.

  1. At the service tool connector, measure the resistance between the terminals for the J1939 data link.

Expected Result:

One of the resistance measurements is an open circuit.

Results:

  • Yes - One of the resistance measurements is an open circuit.

    Repair: Remove the jumper wire from the P1 connector. Determine the cause of the open circuit. Repair the problem, when possible. Replace parts, if necessary. Verify that the problem is resolved.

    STOP

  • No - All of the resistance measurements indicate a short circuit.

    Repair: Remove the jumper wire from the P1 connector.

    Proceed to Test Step 5.

Test Step 5. Check the Termination Resistors for the J1939 Data Link

Note: Perform this test step only if you are troubleshooting a problem with the J1939 data link. Otherwise, proceed to the next Test Step.

  1. At the service tool connector, measure the resistance between the terminals for the J1939 data link.

Expected Result:

The resistance is approximately 120 Ohms.

Results:

  • Yes - The resistance is approximately 120 Ohms. There is a problem with a termination resistor.

    Repair: Determine the cause of the missing termination resistor. Repair the problem, when possible. Replace parts, if necessary. Verify that the problem is resolved.

    STOP

  • No - The resistance is greater than 140 ohms. There is a problem with both termination resistors.

    Repair: Determine the cause of the problem. Repair the problem, when possible. Replace parts, if necessary. Verify that the problem is resolved.

    STOP

  • No - The resistance is between 45 Ohms and 75 Ohms. The termination resistors are OK. Proceed to Test Step 6.

Test Step 6. Disconnect the Modules and Check for Communication

  1. Connect the cables to the vehicle battery.

  1. Identify any additional modules that may be connected to the data links.

  1. Disconnect all of the additional modules from the data link.

  1. Verify that the electronic service tool can communicate with the engine ECM.

  1. Connect a module. Attempt to establish communication between the electronic service tool and the engine ECM. Repeat this Test Step for the remaining modules.

Expected Result:

Communication is lost when a particular module is connected to the data link.

Results:

  • Yes - Communication is lost when a particular module is connected to the data link.

    Repair: Replace the module that is causing the communication to fail. Verify that the problem is resolved.

    STOP

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