3500B Marine Engines Caterpillar

The CAT Data Link is used for communication between electronic modules. The CAT Data Link is used to communicate information from the Electronic Control Module (ECM) to the Electronic Monitoring System (EMS). The CAT Data Link is used for programming and troubleshooting the ECM.

The ECM communicates with the EMS in order to share engine information and diagnostics that may affect engine operation.

The ECM communicates with the Caterpillar Electronic Technician (ET) in order to share status and diagnostic information. The Cat ET can also be used to configure the ECM parameters on the engine. This information will not be available if communications fail between the ECM and the Cat ET.

Illustration 1	g00977405
Typical schematic

Test Step 1. Check for Connector Damage.

1. Turn the circuit breaker for the battery to the OFF position.

2. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.

3. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.

4. Check the ECM connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).

5. Check the customer connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).

6. Check the harness and the wiring for abrasion and for pinch points.

Expected Result:

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

Results:

• OK - The connectors and wiring are okay. Proceed to Test Step 2.

• Not OK - The connectors and/or wiring need repair.

  Repair: Repair the connectors and/or wiring or replace the connectors and/or wiring.

  STOP

Test Step 2. Verify the Problem.

1. Turn the circuit breaker for the battery to the ON position.

2. Turn the ECS to the STOP position. The engine should be OFF.

3. Determine if the EMS displays a random error message or if the EMS displays a CID-FMI 248-12 CAT Data Link malfunction diagnostic code.

4. Determine if the tachometer for the EMS displays a random EE message.

5. The Engine Vision Display shows intermittent error messages under the gauges. The diagnostic screen for the Engine Vision Display does not function properly. The screen for maintenance for the Engine Vision Display does not function properly. A response of "Waiting For ECM" is displayed.

Expected Result:

The EMS displays any of the following errors:

• Random error messages

• A logged CID-FMI 248-12 CAT Data Link malfunction diagnostic code

Results:

• OK - The problem may be in the ECM or in the EMS. Proceed to Test Step 4.

• Not OK - The problem is NOT in the ECM or in the EMS display. Proceed to Test Step 3.

Test Step 3. Install a Data Booster.

1. Turn the ECS to the OFF position.

2. Install a 143-4518 Data Booster on the engine's primary ECM. Refer to the engine schematic for more information.

3. Turn the ECS to the STOP position. The engine should be OFF.

4. Determine if the display module is working properly with the 143-4518 Data Booster.

Expected Result:

The display module should be working properly.

Results:

• OK - The display module is working properly.

  Repair: The problem may be intermittent. If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".

  STOP

• Not OK - The display module is not working properly when the 143-4518 Data Booster is installed.

  Repair: Verify that the connections on the CAT Data Link wires are good. If the connections are good, then temporarily install another data cable run with the 123-2376 Electrical Cable. The combined length should not exceed 30 m (100 ft).

  STOP

Test Step 4. Check the Display Wiring.

1. Turn the circuit breaker for the battery to the ON position.

2. Turn the ECS to the STOP position. The engine should be OFF.

3. Verify that the EMS display is receiving the correct voltage.
   Show/hide table

   Table 1

   EVIM	12-24 VDC
   Engine Vision Display	9-32 VDC
   Engine Vision Display	24 VDC
   EMS Gauge(s)	24 VDC

   Show/hide table

   Table 2

   	Engine Vision Display	Engine Vision Interface Module (EVIM)	Electronic Monitoring System (EMS)	Pilothouse Caterpillar Monitoring System
   + Battery	A	+B	pin 1	pin 1
   -Battery	B	−B	pin 2	pin 2

4. Verify that the CAT Data Link wires are properly installed on the ECM.
   Show/hide table

   Table 3

   	Electronic Monitoring System (EMS)	Engine Vision Interface Module (EVIM)	ECM
   CAT Data Link +	pin 5	+D	P1-9
   CAT Data Link −	pin 14	−D	P1-3

Expected Result:

The EMS, the Pilothouse Caterpillar Monitoring System, and the Engine Vision Interface Module (EVIM) should be receiving 24 ± 3 VDC. The Engine Vision Display should be receiving 9 to 32 VDC. The CAT Data Link wires should be installed properly.

Results:

• OK - The voltage levels are correct. The wiring is installed properly. Proceed to Test Step 5.

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

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

  STOP

• Not OK - There is a problem with the voltage.

  Repair: Refer to the diagnostic functional test Troubleshooting, "Electrical Power Supply".

  STOP

Test Step 5. Check for Electrical Shorts.

1. Turn the ECS to the OFF position. The engine should be OFF.

2. Turn the circuit breaker for the battery to the OFF position.

3. Disconnect the ECM connectors for the primary ECM and for the secondary ECM.

4. Disconnect the EMS, the pilothouse caterpillar monitoring system, and the Engine Vision Interface Module (EVIM) from the CAT Data Link.

5. Measure the resistance at the following points. Wiggle the harness during the measurement in order to reveal an intermittent short.

   • CAT Data Link + to CAT Data Link −

   • CAT Data Link + to − Battery terminal

   • CAT Data Link − to − Battery terminal

   • CAT Data Link + to + Battery terminal

   • CAT Data Link − to + Battery terminal

   • CAT Data Link + to engine ground

   • CAT Data Link − to engine ground

Expected Result:

The resistance should read more than 20,000 Ohms for each measurement.

Results:

• OK - The resistance is greater than 20,000 Ohms. Proceed to Test Step 6.

• Not OK - The resistance is less than 20,000 Ohms. There is a short in the harness or in the connectors.

  Repair: Repair the connector and/or wiring or replace the connector and/or wiring.

  STOP

Test Step 6. Check the Resistance through the Harness for an Open Circuit.

1. Turn the ECS to the OFF position. The engine should be OFF.

2. Turn the circuit breaker for the battery to the OFF position.

3. Disconnect the ECM connectors for the primary ECM and for the secondary ECM.

4. Disconnect the EMS, the pilothouse caterpillar monitoring system, and the EVIM from the CAT Data Link.

5. Short the wires of the CAT Data Link together. Create the short at P1-9 and P1-3 of the primary ECM connector.

6. Set an ohmmeter on the 200 ohm scale. Measure the resistance between the terminals of the CAT Data Link + and the CAT Data Link − at the display connectors. Wiggle the harness during the measurements in order to reveal an intermittent open condition.

Expected Result:

The resistance should be less than 5 Ohms for each measurement.

Results:

• OK - The resistance is less than 5 Ohms for each measurement.

  Repair: The harness is okay. There could be a problem with the display or with the ECM. Connect the display on another engine. If the problem returns on the other engine, replace the display. If the problem does not return, replace the ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM".

  STOP

• Not OK - The resistance is greater than 5 Ohms for each measurement.

  Repair: There is an open circuit or there is excessive resistance in the harness. Repair the connectors and/or wiring or replace the connectors and/or wiring.

  STOP