3500B Engines for Caterpillar Built Power Modules with the ADEM 3 Electronic Control Module Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the circuit for the CAN data link or if the diagnostic code in Table 1 is active or easily repeated.

The CAN data link is used for communication between the following modules: engine's Electronic Control Module (ECM), customer devices and various display modules. Two 120 Ohm terminating resistors must be installed in the wiring harness in order for the CAN data link to function properly.

Illustration 1	g01443619
Typical example

Test Step 1. Check for Connector Damage.

1. Turn the battery disconnect switch to the OFF position.

2. Turn the breaker to the OFF position.

3. 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.

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

5. Check the ECM connectors (allen head screw) for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.

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. The harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

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

• Not OK - The connectors and/or wiring are not OK.

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

  STOP

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

1. Verify that the terminating resistors are installed on the ends of the data link.

2. Disconnect J1/P1 ECM connector and measure the resistance between P1-50 (CAN data link +) and P1-34 (CAN data link -).

Expected Result:

The resistance is approximately 60 ± 3 Ohms.

Results:

• OK - The resistance is within the range. Proceed to Test Step 3.

• Not OK - The resistance is approximately 120 ± 6 Ohms. A terminating resistor is missing or damaged.

  Repair: If a termination resistor is missing, install the missing resistor. If both resistors are present, measure the resistance between pin A and pin B of the termination resistor. The resistance should measure 120 ± 3 Ohms. Replace the termination resistor if the resistance is not 120 ± 3 Ohms.

  Refer to the schematic in order to determine the missing resistor.

  Verify that the repair eliminates the problem.

  STOP

Test Step 3. Check for a Short Circuit in the Harness.

1. Disconnect the J1/P1 ECM connector, the generator connector , and the thermocouple connector.

2. Remove the terminating resistors from the harness for the CAN data link.

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

3. Measure the resistance between P1-50 (CAN data link +) and the remaining terminals on the P1 connector.

4. Measure the resistance between P1-50 (CAN data link +) and the engine ground.

5. Measure the resistance between Pin-35 (CAN data link +) and the remaining terminals on the generator connector.

6. Measure the resistance between Pin-35 (CAN data link +) and the engine ground.

Expected Result:

The resistance is greater than 20000 Ohms.

Results:

• OK - The resistance is greater than 20000 Ohms. Proceed to Test Step 4.

• Not OK - The resistance is less than 20000 Ohms.

  Repair: There is a short in the harness wiring. Repair the connectors or wiring and/or replace the connectors or wiring.

  Verify that the repair eliminates the problem.

  STOP

Test Step 4. Check for an Open Circuit in the Harness.

1. All connections should remain disconnected.

2. Fabricate a jumper wire. Short pin G and pin F on the service tool connector.

3. Measure the resistance between Pin-35 (CAN data link +) and Pin-36 (CAN data link -) at the generator connector.

4. Short pin 2 and pin 3 on the thermocouple connector.

5. Measure the resistance between Pin-35 (CAN data link +) and Pin-36 (CAN data link -) at the generator connector.

6. Short pin A and pin B on any remaining connectors in the generator connector circuit.

7. Measure the resistance between Pin-35 (CAN data link +) and Pin-36 (CAN data link -) at the generator connector.

8. Short pin A and pin B on any connectors in the ECM circuit.

9. Measure the resistance between P-50 (CAN data link +) and P-34 (CAN data link -) at the ECM connector.

Expected Result:

The resistance is less than five Ohms.

Results:

• OK - The resistance is less than five Ohms.

  Repair: The harness for the CAN data link is OK.

  STOP

• Not OK - The resistance is greater than five Ohms.

  Repair: There is an open in the harness wiring. Repair the connectors or wiring and/or replace the connectors or wiring. Make the necessary repairs.

  Verify that the repair eliminates the problem.

  STOP