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G3520B Industrial Engines Caterpillar


CAN Data Link - Test

Usage:

G3520B GLF
System Operation Description:

Use this procedure to troubleshoot a suspected problem with the CAN data link or use this procedure if one of the diagnostic codes in Table 1 are active or easily repeated.

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Table 1
Diagnostic Codes Table    
Description     Conditions which Generate this Code     System Response    
1440-9 Throttle Actuator : Abnormal Update Rate     The ECM has lost the last ten messages that were expected from the actuator for the throttle over the CAN data link.     The code is logged.
The alarm output is activated.
The shutdown output is activated.
The engine is shut down.    
1446-9 Fuel Metering Module : Abnormal Update Rate     The ECM has lost the last ten messages that were expected from the fuel metering valve over the CAN data link.     The code is logged.
The alarm output is activated.    
1720-9 Turbocharger Compressor Bypass Valve Actuator : Abnormal Update Rate     The ECM has lost the last four messages that were expected from the compressor bypass actuator over the CAN data link.     The code is logged.
The alarm output is activated.
The shutdown output is activated.
The engine is shut down.    
3002-9 Engine Exhaust NOx Level Sensor : Abnormal Update Rate     The ECM has lost the last ten messages that were expected from the NOX level sensor over the CAN data link.     The code is logged.
The alarm output is activated.    

The CAN data link is used to communicate information between the master ECM and other control modules that are on the engine. 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 display panel

A -9 code that is related to any specific control module may be caused by the power supply circuit to the control module. Be sure to check that the suspect control module is receiving the power before you troubleshoot the circuit for the CAN data link. If you suspect that a power supply circuit may be the cause of the -9 code, refer to the circuit test for the suspect control module and troubleshoot the problem.

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

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Illustration 1g01580854

Schematic for the CAN data link

Test Step 1. Inspect the Electrical Connectors and the Wiring

  1. Remove the electrical power from the ECM.
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    Illustration 2g01424765

    Location of the ECM connectors for the CAN data link (typical left side engine view)

    (1) Termination resistor

    (2) J1/P1 ECM connectors

    (3) J5/P5 customer connectors

    (4) J8/P8 control harness connectors

    (5) P10 connector for the harness to the optional control panel

  1. Thoroughly inspect ECM connectors (1). Inspect all of the connectors that are associated with the CAN data link. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
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    Illustration 3g01412137

    Terminal locations at the P1 ECM connector that are associated with the CAN data link

    (P1-34) CAN data link −

    (P1-42) CAN shield

    (P1-50) CAN data link +

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    Illustration 4g01412144

    Terminal connections at the P5 connector that are for the fuel metering valve

    (P5-53) CAN data link +

    (P5-54) CAN data link −

    (P5-55) CAN shield

    (P5-63) CAN data link +

    (P5-64) CAN data link −

    (P5-65) CAN shield

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    Illustration 5g01424850

    Terminal locations at the P8 connector that are for the fuel metering valve

    (P8-h) CAN shield

    (P8-O) CAN data link +

    (P8-Y) CAN data link −

    Show/hide table

    Illustration 6g01424853

    Terminal locations at the P10 connector that are for the fuel metering valve

    (P10-F) CAN data link +

    (P10-L) CAN data link −

    (P10-V) CAN shield

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    Illustration 7g01424819

    Terminal locations at the fuel metering valve for the CAN data link and the termination resistor (jumper)

    (Terminal C) CAN Data Link +

    (Terminal F) CAN Data Link −

    (Terminal P) Termination resistor (jumper)

    (Terminal R) Termination resistor (jumper)

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    Illustration 8g01424902

    Terminal locations for the CAN data link at the compressor bypass actuator and throttle actuator

    (Terminal C) CAN shield

    (Terminal G) CAN data link −

    (Terminal M) CAN data link +

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    Illustration 9g01424907

    Terminal locations for the CAN data link at the NOX sensor buffer

    (Terminal 3) CAN Data Link −

    (Terminal 4) CAN Data Link +

    Show/hide table

    Illustration 10g01424780

    Terminal locations at the connector for the termination resistor that are associated with the CAN data link

    (Terminal 1) CAN data link +

    (Terminal 3) CAN shield

    (Terminal 4) 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 and 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 OK. 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. Remove the electrical power from the ECM.

  1. Disconnect the following components from the data link:

    • ECM at the P1 ECM connector

    • Bypass valve actuator

    • NOX sensor buffer

    • Optional display panel

    • Throttle actuator

    Do not disconnect the fuel metering valve from the data link.

    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.

    Repair: A termination resistor is missing. One resistor must be located on each end of the data link. Verify that the termination resistor that is in the terminal box for the master ECM is connected to the data link. The other termination resistor is an internal resistance that is located in the fuel metering valve. Ensure that the harness connector is connected to the fuel metering valve. Ensure that the jumper wire that is used to enable the internal resistance is connected between terminals P and R at the harness connector for the fuel metering valve.Refer to the appropriate Electrical Schematic in order to determine the missing resistor. Replace the missing resistor. Restore the wiring to the original configuration. Verify that the problem is resolved.

    STOP

  • Not OK - The resistance is less than 57 Ohms. There may be a short circuit in the harness. Leave the jumper wires in place. Proceed to Test Step 3.

  • Not OK - The resistance is greater than 126 Ohms. There may be an open circuit in the harness. Leave the jumper wires in place. Proceed to Test Step 4.

Test Step 3. Check the Harness for a Short Circuit

  1. Remove the termination resistor that is located in the terminal box for the master ECM from the CAN data link.

  1. Disconnect the harness connector from the fuel metering valve.

  1. Measure the resistance between the points that are listed in Table 2. Be sure to wiggle the wires in the harnesses as you make each resistance measurement.

    Show/hide table
    Table 2
    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    
    ECM ground strap
    P1-34 (CAN data link -)     All of the other terminals on the P1 connector    
    ECM ground strap

Expected Result:

Each check of the resistance indicates an open circuit.

Results:

  • OK - Each check of the resistance indicates an open circuit. The harness is not shorted. Proceed to Test Step 4.

  • Not OK - At least one check of the resistance indicates that there is continuity in the circuit.

    Repair: There is a short circuit in a harness. There may be a problem with a connector. Repair the wiring and/or the connector. Replace part, if necessary. Restore the wiring to the original configuration. Verify that the problem is resolved.

    STOP

Test Step 4. Check the Harness for an Open Circuit

  1. Remove the termination resistor that is located in the terminal box for the master ECM from the CAN data link.

  1. Disconnect the harness connector from the fuel metering valve.

  1. Fabricate a jumper wire that is long enough to create a test circuit across the connector for the termination resistor. Crimp connector pins to each end of the jumper wire.

  1. Use the jumper wire in order to create a short circuit between terminals 1 and 4 at the harness connector for the termination resistor that is located in the terminal box for the master ECM. This will effectively replace the termination resistor with a short circuit.

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

    • Terminals P1-34 and P1-50 at the ECM connector

    • Terminals 3 and 4 at the harness connector for the NOX sensor buffer

    • Terminals F and C at the harness connector for the fuel metering valve

  1. Remove the jumper wire.

  1. 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 that is located on the customer's harness after the engine interface connector. This will effectively replace the termination resistor with a short circuit.

  1. Restore the wiring to the original configuration. Connect the termination resistor to the data link.

Expected Result:

The resistance measurement indicates that a short circuit exists while the jumper wire is in place.

Results:

  • OK - A short circuit exists while the jumper wire is in place.

    Repair: The wiring for the CAN data link is OK. There appears to be a problem with the ECM. Perform the following procedure:

    1. Temporarily connect a new ECM.

      Refer to Troubleshooting, "ECM - Replace " for details.

    1. Recheck the circuit in order to ensure that the original problem has been resolved.

      If the problem is resolved with the new ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved.

      If the problem is not resolved with the new ECM, install the original ECM. There is a problem in the wiring. Perform the necessary repairs. Verify that the repair has resolved the original condition.

    STOP

  • Not OK - An open circuit exists for at least one of the measurements while the jumper wire is in place.

    Repair: There is an open circuit or excessive resistance in the circuit. There may be a problem in a connector. Repair the wiring and/or the connector. Replace parts, if necessary. Verify that the problem is resolved.

    STOP

Test Step 5. Check for Customer Installed Components on the CAN Data Link

  1. Check if other customer installed components have been installed on the data link.

  1. Verify the operation of the components before proceeding. Refer to OEM information for the individual components.

Expected Result:

The customer installed components operate properly.

Results:

  • OK - The customer installed components operate properly.

    Repair: Reconnect the component to the engine. If the component operates correctly, there may be a problem with an electrical connector. Refer to Troubleshooting, "Electrical Connectors - Inspect".If the component 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. If the operation of the customer installed component has been verified and the diagnostic code remains active, replace the ECM. Refer to Troubleshooting, "ECM - Replace ".

    STOP

  • Not OK - The customer installed components do not operate properly.

    Repair: Replace the component. Verify that the problem is resolved.

    STOP

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