C32 Marine Engines CAN Data Link Circuit - Test Caterpillar


CAN Data Link Circuit - Test
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System Operation Description:

The CAN data link is used to communicate information between the Electronic Control Module (ECM) and other modules. Use this procedure to troubleshoot any suspect problems with the CAN data link.

This procedure identifies the following problems:

  • Faulty connectors

  • Missing termination resistors

  • Short circuits

  • Open circuits

  • Faulty marine power display

A problem with the CAN data link is probably caused by a short circuit to ground or a short circuit to another voltage source in the harness. The next likely cause is a problem with a module that is connected to the data link. The least likely cause is a problem with the ECM.




Illustration 1g01136702

Schematic for the CAN data link

Test Step 1. Inspect the Electrical Connectors and the Wiring

  1. Turn the keyswitch to the OFF position.



    Illustration 2g01130302

    Engine components for the CAN data link

    (1) J1/P1 connectors

    (2) Termination resistor

    (3) J60 connector for the electronic service tool

    (4) J61 customer connector

  1. Thoroughly inspect connectors (1). Inspect all of the connectors that are associated with the CAN data link. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.



    Illustration 3g01091318

    P1 terminals that are associated with the CAN data link

    (P1-34) CAN data link −

    (P1-42) CAN shield

    (P1-50) CAN data link +

  1. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the CAN data link.

  1. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

  1. Check the allen head screw on the customer connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

  1. Check the wiring harnesses for abrasion, for corrosion and for pinch points.

Expected Result:

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

Results:

  • OK - The harness and wiring appear to be okay. Proceed to Test Step 2.

  • Not OK - There is a problem in the wiring harness.

    Repair: Repair the connectors and/or the wiring. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the problem is resolved.

    STOP

Test Step 2. Verify the Proper Installation of the Termination Resistors

  1. Turn the keyswitch to the OFF position.

  1. Disconnect the Marine Power Display (MPD).

  1. Disconnect the AVSpare Electronic Technician (Cat ET) from the service tool connector.

  1. Disconnect the P1 connector.

    Note: Wiggle the harness during the following measurements in order to reveal an intermittent condition.

  1. Measure the resistance between terminals P1-50 (CAN Data Link +) and P1-34 (CAN Data Link -).

Expected Result:

The resistance is between 57 and 63 Ohms.

Results:

  • OK - The resistance is between 57 and 63 Ohms. Proceed to Test Step 3.

  • Not OK - The resistance is between 114 Ohms and 126 Ohms. A termination resistor is missing.

    Repair: Verify that two termination resistors are connected to the data link. One resistor must be located on each end of the data link. The engine is shipped with one termination resistor that is installed between the ECM and the customer connector.Refer to the appropriate electrical schematic in order to determine the missing resistor. Replace the missing resistor. Verify that the problem is resolved.

    STOP

  • Not OK - The resistance is less than 57 Ohms. Proceed to Test Step 3.

  • Not OK - The resistance is greater than 126 Ohms. Proceed to Test Step 4.

Test Step 3. Check for a Short Circuit

  1. Remove both termination resistors from the CAN data link.

  1. Disconnect the marine power display.

  1. Measure the resistance between the points that are listed in Table 1. Be sure to wiggle the wires in the harnesses as you make each resistance measurement.

    Table 1
    Resistance Measurements for the CAN Data Link    
    Connector and Terminal     Terminal    
    P1-50 (CAN data link +)     All of the other terminals on the P1 connector    
    Engine ground
    P1-34 (CAN data link -)     All of the other terminals on the P1 connector    
    Engine ground

Expected Result:

Each check of the resistance indicates an open circuit.

Results:

  • OK - Each check of the resistance indicates an open circuit. Proceed to Test Step 4.

  • Not OK - At least one check of the resistance does not indicate an open circuit. There is a short circuit in a harness. There may be a problem with a connector.

    Repair: Repair the wiring and/or the connector. Replace part, if necessary. Verify that the problem is resolved.

    STOP

Test Step 4. Check for an Open Circuit

  1. Remove the termination resistor from the end of the tee.

  1. Fabricate a jumper wire. Use the jumper wire in order to create a short circuit between terminals A and B on the tee's connector for the termination resistor. This will replace the termination resistor with a short circuit.

  1. Measure the resistance between terminals P1-50 (CAN data link +) and P1-34 (CAN data link -).

  1. Remove the jumper wire from the tee. Connect the termination resistors to the data link.

  1. Connect the J1/P1 connectors.

Expected Result:

The resistance is less than ten Ohms.

Results:

  • OK - The resistance is less than ten Ohms. There is not an open circuit. Proceed to Test Step 5.

  • Not OK - The resistance is more than ten Ohms. There is an open circuit or excessive resistance in the circuit. There may be a problem in a connector.

    Repair: Repair the wiring and/or the connector. Replace part, if necessary. Verify that the problem is resolved.

    STOP

Test Step 5. Check the Marine Power Display

  1. Connect the marine power display to another engine.

  1. Operate the engine and monitor the marine power display.

Expected Result:

The marine power display operates properly.

Results:

  • OK - The marine power display operates properly on another engine.

    Repair: Connect the display to the original engine. If the display operates correctly, there may be a problem with an electrical connector. Refer to Troubleshooting, "Electrical Connectors - Inspect".If the display does not operate correctly on the original engine, there may be a problem with the ECM.It is unlikely that the ECM has failed. Perform this entire procedure again. Replace the ECM if the display still does not operate correctly. Refer to Troubleshooting, "Replacing the ECM".

    STOP

  • Not OK - The marine power display does not operate properly on another engine.

    Repair: Replace the marine power display. Verify that the problem is resolved.

    STOP

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