HEAD 1206680 - Caterpillar

System Operation Description: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 g01199117
Typical example
Illustration 2 g01241421
P1 ECM connector
(P1-34) CAN data link −
(P1-42) Shield for the CAN data link
(P1-50) CAN data link +
Illustration 3 g01241422
Service tool connector
(Terminal C) Shield for the CAN data link
(Terminal F) CAN data link +
(Terminal G) CAN data link −
Illustration 4 g01241424
Customer connector
(Terminal BT) Shield for the CAN data link
(Terminal BV) CAN data link +
(Terminal BU) CAN data link −
Illustration 5 g01234146
Location of ECM connectors
Test Step 1. Inspect Electrical Connectors and Wiring
Turn the Engine Control Switch (ECS) to the OFF/RESET position.
Turn the battery disconnect switch to the OFF position.
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.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for the correct torque values.
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.STOPTest Step 2. Verify the Proper Installation of the Terminating Resistors
Verify that the terminating resistors are installed on the ends of the 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. 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.STOPTest Step 3. Check for a Short Circuit in the Harness
Disconnect the J1/P1 ECM connector.
Remove the terminating resistors from the harness for the CAN data link.
If a Marine Power Display (MPD) is installed, disconnect the MPD.
Measure the resistance between the following pins.
P1-50 (CAN data link +) and +Battery
P1-34 (CAN data link -) and +Battery
P1-50 (CAN data link +) to P1-34 (CAN data link -)
P1-50 (CAN data link +) to P1-42 (CAN data link shield)
P1-34 (CAN data link -) to P1-42 (CAN data link