G3520B Engines Caterpillar

The Cat data link is used to share information between the following components:

• Master Electronic Control Module (ECM)

• Slave ECM

• Integrated Temperature Sensing Module (ITSM)

• Service tool

• Customer installed components

Illustration 1 shows the information that is shared between the master ECM and the slave ECM via the Cat data link.

Illustration 1	g00951847

Each ECM and the ITSM communicate with Cat ET via the Cat data link. The Cat data link consists of two wires that are twisted together. One wire is designated as +. The other wire is designated as -. The signals on the data link wires are a square wave type signal. The signals operate at a very high frequency. The signals cannot be measured with common service tools. Therefore, only continuity measurements can be made on the wires for the Cat data link.

The most likely cause of a diagnostic code for the Cat data link are an open circuit or a short circuit. Connector terminals that are not fully seated in the connector body can create an open circuit condition. Be careful not to interchange the + wire and the - wire in a connector. The Cat data link will not operate if the + wire and the - wire are interchanged in a connector.

The Cat data link can fail if a module is not receiving power. This can happen if there is a problem with the wiring that provides power to the module.

The Cat data link can fail if a module is programmed with the wrong FLASH file, or if a module has not been programmed with a FLASH file. Verify that all modules have been programmed with the proper FLASH file.

Harness Code for the Slave ECM

The harness inside the terminal box has a jumper wire (harness code) that connects terminals J3-29 and J3-60. The ECM that is connected to the harness reads the harness code. This allows the ECM to operate as the slave ECM.

If the jumper wire is disconnected, the slave ECM will assume the function of a master ECM. Cat ET will not communicate with any of the modules. Cat ET will display "DupliCate Type on data link. Unable to Service".

Illustration 2	g00994089
Schematic diagram of the Cat data link

Test Step 1. Inspect the Electrical Connectors and wiring

1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".

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Illustration 3	g00920000
Terminal box for the master ECM (1) Ground strap (2) J1/P1 connectors for the master ECM (3) J23 connector for Cat ET (4) J19 connector (5) 16 amp circuit breaker (6) J5/P5 connectors for the harness to the ITSM (7) J8/P8 connectors for the harness to the slave ECM (8) J9/P9 connectors

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Illustration 4	g00920005
Terminal box for the slave ECM (9) J3/P3 connectors for the slave ECM (10) J20/P20 connectors for the harness to the master ECM

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Illustration 5	g00920007
ITSM (11) ITSM (12) J18/P18 connectors for the harness to the terminal box for the master ECM

2. Thoroughly inspect each of the following connectors:
   • Master ECM J1/P1 connectors

   • J23, J5/P5, J8/P8, J9/P9 and J19 connectors on the terminal box for the master ECM

   • J3/P3 connectors for the slave ECM

   • J20/P20 connectors on the terminal box for the slave ECM

   • J18/P18 connectors for the ITSM

   1. Check the torque of the Allen head screw for the ECM connectors. The proper torque is 6 ± 1 N·m (53 ± 9 lb in).
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   Illustration 6	g00994115
   Harness side of the master ECM P1 connector and the P3 connector for the slave ECM (P1-8) Cat data link + (P1-9) Cat data link −

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   Illustration 7	g00994117
   Harness side of the P3 connector for the slave ECM (P3-8) Cat data link + (P3-9) Cat data link − (P3-29) Harness code (P3-60) harness code

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the Cat data link.

   3. Check the harness and wiring for abrasion and for pinch points from the slave ECM to the master ECM.

   4. Check the wiring harness from the P9 connector to the optional remote control panel.

Expected Result:

The connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.

Results:

• OK - The components are in good condition with proper connections. Proceed to Test Step 2.

• Not OK - The components are not in good condition and/or at least one connection is improper.

  Repair: Perform the necessary repairs and/or replace parts, if necessary.

  STOP

Test Step 2. Check the Cat Data Link

1. Verify that the engine control is in the OFF/RESET mode. Verify that the 16 amp circuit breaker is OFF.

2. Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".

3. Set the engine control to the STOP mode. Switch the 16 amp circuit breaker ON.

4. Select the "File/Select ECM" menu on the Cat ET. Verify that all of the modules are displayed on the "ECM Selector" screen.

   Verify that the following diagnostic codes are not activated.

   • 0590-09 Unable to communiCate with Engine ECM

   • 1636-09 Loss of communiCation with Engine #2 (Slave)

   • 1042-09 Unable to communiCate with ITSM

   Note: If Cat ET displays "DupliCate Type on data link. Unable to Service", there may be a problem with the harness inside the terminal box for the slave ECM. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF. Check the continuity between terminals J3-29 and J3-60. Verify that the jumper wire is in good condition. Make repairs, as needed.

Expected Result:

All of the modules are displayed on the "ECM Selector" screen. There are no active diagnostic codes for the Cat data link.

Results:

• OK - All of the modules are displayed on the "ECM Selector" screen. There are no active diagnostic codes for the Cat data link. The problem seems to be resolved.

  Repair: If any of the above codes are logged and the engine is not running properly, refer to Troubleshooting, "Troubleshooting Without a Diagnostic Code".If any of the above codes are logged and the engine is running properly, there may be an intermittent problem in a connector or a wiring harness. Refer to Troubleshooting, "Inspecting Electrical Connectors".

  STOP

• Not OK - At least one of the modules is not displayed on the "ECM Selector" screen. There may be an active diagnostic code for the Cat data link. Proceed to Test Step 3.

Test Step 3. Check the Wiring for the Cat Data Link

1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

2. Disconnect Cat ET from the service tool connector.

3. Disconnect the following connectors:
   • P1 connector from the master ECM

   • P3 connector from the slave ECM

   • P9 connector from the terminal box

   • P18 connector from the ITSM

4. Measure the resistance between the points that are listed in Table 1. During each measurement, wiggle the wires in the harness in order to check for an intermittent problem. Be sure to wiggle the wires near each of the connectors.

Expected Result:

Each check of the resistance between the connectors is less than 5 ohms.

Each check of the resistance between the connector and the ground strap is greater than 20,000 ohms.

Results:

• OK - Each check of the resistance for the Cat data link is within the specification. The wiring for the Cat data link appears to be OK.

  Repair: Perform the following procedure:

  1. Connect the following connectors:
     • P1 connector to the master ECM

     • P3 connector to the slave ECM

     • P9 connector

     • 14-pin connector to the ITSM

  2. Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".

  3. Switch the 35 amp circuit breaker ON. Set the engine control to the STOP mode.

  4. Verify that Cat ET is able to communicate with each of the modules.

  5. If Cat ET is unable to communicate with a module, there may be a problem with the supply voltage to the module. Refer to Troubleshooting, "Electrical Power Supply".

  6. If the problem is not resolved, there may be a problem with the wiring for the Cat data link between the J9 connector and the customer's equipment. Verify that the wiring for the Cat data link between the J9 connector and the customer's equipment is working properly.

  7. If the problem is not resolved, there may be a problem with the module that is not communicating with Cat ET.

     It is unlikely that a module has failed. Exit this procedure and perform this procedure again. If the problem is not resolved, temporarily replace the module that is not communicating. Refer to Troubleshooting, "Replacing the ECM" or Troubleshooting, "Replacing the ITSM". Verify that the problem is resolved.

     If the problem is resolved with the new module, reinstall the original module and verify that the problem returns. If the new module works correctly and the original module does not work correctly, replace the original module. Refer to Troubleshooting, "Replacing the ECM" or Troubleshooting, "Replacing the ITSM".

  STOP

• Not OK - At least one check of the resistance for the Cat data link is incorrect. There is a problem with the wiring for the Cat data link.

  Repair: Repair the connection and/or the wire, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP