GUARD AS 2626094 - Caterpillar

The CAN Data Link is used to communicate information from the ECM in order to share engine information and diagnostics for the electronic system.
Illustration 1 g00855398
Schematic for the CAN Data Link
Illustration 2 g00894367
P1 ECM connectorTest Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF/RESET position.
Check the connectors and wiring for the following problems: damage, corrosion, abrasion and incorrect attachment. Pay close attention to the following areas:
J1/P1 ECM connector
J3/P3 Customer connector
Connectors for the J1939 Data Link
Engine wiring harness from the ECM to the customer connectorRefer to Troubleshooting, "Electrical Connectors - Inspect" for more information.Expected Result:The connectors and wiring should be free of the following problems: damage, corrosion, abrasion and incorrect attachment.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Repair the J1939 Data Link circuit. Verify that the repair eliminates the problem. Stop.Test Step 2. Verify that Termination Resistors are Installed on the Ends of the Data Link
Disconnect P1 from the ECM.
Disconnect the J1939 Displays from the harness.
Measure the resistance between P1:10 and P1:16 of the P1 ECM connector.Expected Result:The resistance should be 60 ohms 5%.Results:
OK - Proceed to Test Step 3.
Not OK - Repair: The resistance equals 120 ohms 5%. A terminating resistor is missing. Refer to Illustration 1 and install the missing terminating resistor. Stop.
Not OK - Resistance is less than 50 ohms. Proceed to Test Step 3.
Not OK - Resistance is greater than 130 ohms. Proceed to Test Step 4.Test Step 3. Verification of Number of Terminating ResistorsA terminating resistor should be installed at each end of the J1939 data link. Refer to Illustration 1 for the proper location.Expected Result:The J1939 Data Link circuit should contain two terminating resistors.Results:
OK - Proceed to Test Step 4.
Not OK - Make the necessary changes in the circuit for the J1939 Data Link in order to ensure that the two terminating resistors are in the proper locations. Stop.Test Step 4. Check for a Short in the CAN Data Link
Disconnect P1 from the ECM.
Disconnect the J1939 display modules.
Remove the terminating resistors.
Measure the resistance between the following pins.
P1:10 and P1:16
P1:10 and P1:15
P1:15 and P1:16Expected Result:The resistance should be greater than 20,000 ohms.Results:
OK - There are no shorts in the wiring harness. Proceed to Test Step 5.
Not OK - Repair: There is a short in the harness. Make the necessary repairs. Verify that the repair eliminates the problem. Stop.Test Step 5. Check for an Open Circuit at the J1939 Display
Allow the components to remain disconnected.
Make a short jumper with sockets.
Install one end of the jumper on pin A of the J1939 Display connector.
Install the other end of the jumper to pin B of the J1939 Display connector.
Measure the resistance between P1:10 and P1:16.Expected Result:The resistance should be less than 10 ohms.Results:
OK - Proceed to Test Step 6.
Not OK - Repair: There is an open circuit in the harness. Make the necessary repairs. Verify that the repair eliminates the problem. Stop.Test Step 6. Check the J1939 Display
Reconnect the P1 ECM connector.
Remove the J1939 Display and take the display to the