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.
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| Illustration 1 | g01443036 |
Typical example | |
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| Illustration 2 | g01444508 |
Location of the ECM connectors (1) J2/P2 ECM connectors (2) J1/P1 ECM connectors | |
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| Illustration 3 | g01443030 |
P1 ECM connector (P1-34) J1939 data link − (P1-42) J1939 shield (P1-50) J1939 data link + (P1-60) Digital reference | |
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| Illustration 4 | g01443042 |
Generator connector (Terminal 35) CAN data link + (Terminal 36) CAN data link − (Terminal 38) CAN data link (shield) | |
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| Illustration 5 | g01241422 |
Service tool connector (Terminal C) Shield for the CAN data link (Terminal F) CAN data link + (Terminal G) CAN data link − | |
Test Step 1. Inspect Electrical Connectors and Wiring
- Turn the Engine Control Switch (ECS) to the OFF/RESET position. Turn the main disconnect switch to the OFF position.
- Thoroughly inspect the J1/P1 ECM connector and the J2/P2 ECM connector. Inspect all of the connectors that are associated with the circuit.
Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.
- Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
- Check the harness and 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 or 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: Perform the following repair:Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Refer to Troubleshooting, "Electrical Connectors - Inspect".Verify that the repair eliminates the problem.
STOP
Test Step 2. Verify the Proper Installation of the Data Link Circuit
- Disconnect any module that is connected to the CAN data link.
- 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.
Repair: If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".
STOP
- 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.
STOP
- Not OK - Resistance is less than 57 Ohms. Proceed to Test Step 3.
- Not OK - Resistance is greater than 126 Ohms. Proceed to Test Step 4.
Test Step 3. Check for a Short Circuit
- Remove the terminating resistors from the CAN data link.
- Measure the resistance from the following pins to every pin on ECM connector P1 and to engine ground.
- P1-50 (CAN data link +)
- P1-34 (CAN data link -)
- P1-42 (CAN shield)
- P1-60 (Digital reference)
- P1-50 (CAN data link +)
Expected Result:
Each resistance measurement indicates an open circuit.
Results:
- OK - There are no shorts. Proceed to Test Step 4.
- Not OK - A short exists in the wiring harness.
Repair: Make the necessary repairs.Verify that the repair eliminates the problem.
STOP
Test Step 4. Check for an Open Circuit
- Make sure that all connections remain disconnected.
- Fabricate a jumper wire. Use the jumper wire in order to short pin F to pin G on the service tool connector.
- Measure the resistance between P1-35 (CAN data link +) and P1-36 (CAN data link -) at the generator connector.
- Use the jumper wire in order to short pin 2 to pin 3 on the thermocouple connector.
- Measure the resistance between P1-50 (CAN data link +) and P1-34 (CAN data link -) at the ECM connector.
- Use the jumper wire in order to short pin A to pin B on any remaining connectors in the circuit.
- Measure the resistance between P1-35 (CAN data link +) and P1-36 (CAN data link -) at the generator connector or measure the resistance between P1-50 (CAN data link +) and P1-34 (CAN data link -) at the ECM connector.
- Remove the jumper wires.
Expected Result:
The resistance measurement indicates a short circuit.
Results:
- OK - There is not an open circuit.
Repair: If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".
STOP
- Not OK - An open circuit exists in the wiring harness.
Repair: Make the necessary repairs.Verify that the repair eliminates the problem.
STOP