5035574 JOHNSON PIN

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Schematic for the CAN data linkTest Step 1. Inspect the Electrical Connectors and the Wiring
Remove the electrical power from the ECM.
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Location of the ECM connectors for the CAN data link (typical left side engine view) (1) J1/P1 ECM connectors
Thoroughly inspect ECM connectors (1). Inspect all of the connectors that are associated with the CAN data link. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
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Terminal locations at the P1 ECM connector that are associated with the CAN data link (P1-34) CAN data link − (P1-42) CAN shield (P1-50) CAN data link +
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Terminal locations at the service tool connector that are associated with the CAN data link (Terminal C) CAN shield (Terminal F) CAN data link + (Terminal G) CAN data link −
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Terminal locations at the connector for the termination resistor that are associated with the CAN data link (Terminal A) CAN data link + (Terminal B) CAN data link − (Terminal C) CAN shield
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the CAN data link.
Check the allen head screw on each ECM connector and on the customer connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the wiring harnesses for abrasion, for corrosion 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 harness and wiring appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem in the wiring harness.Repair: Repair the connectors and/or the wiring. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the problem is resolved.STOPTest Step 2. Verify the Proper Installation of the Termination Resistors
Remove the electrical power from the ECM.
Disconnect any display panel from the data link.
Disconnect the Caterpillar Electronic Technician (ET) from the service tool connector.
Disconnect the P1 ECM connector.Note: Wiggle the harness during the following measurements in order to reveal an intermittent condition.
Measure the resistance between terminals P1-50 (CAN data link +) and P1-34 (CAN data link -).Expected Result:The resistance is between 57 and 63 Ohms.Results:
OK - The resistance is between 57 and 63 Ohms. Proceed to Test Step 3.
Not OK - The resistance is between 114 Ohms and 126 Ohms. A termination resistor is missing.Repair: Verify that two termination resistors are connected to the data link. One resistor must be located on each end of the data link. The engine is shipped with one termination resistor that is installed between the ECM and the customer connector.Refer to the appropriate electrical schematic in order to determine the missing resistor. Replace the missing resistor. Verify that the problem is resolved.STOP
Not OK - The resistance is less than 57 Ohms. There may be a short circuit in the harness. Proceed to Test Step 3.
Not OK - The resistance is greater than 126 Ohms. There may be an open circuit in the harness. Proceed to Test Step 4.Test Step 3. Check the Harness for a Short Circuit
Remove both termination resistors from the CAN data link.
Disconnect the display panel.
Measure the resistance between the points that are listed in Table 1. Be sure to wiggle the wires in the harnesses as you make each resistance measurement.
Table 1
Resistance Measurements for the CAN Data Link    
Connector and Terminal    Terminal    
P1-50 (CAN data link +)     All of the other terminals on the P1 connector    
Engine ground
P1-34 (CAN data link -)     All of the other terminals on the P1 connector    
Engine ground Expected Result:Each check of the resistance indicates an open circuit.Results:
OK - Each check of the resistance indicates an open circuit. The harness is not shorted. Proceed to Test Step 4.
Not OK - At least one check of the resistance does not indicate an open circuit.Repair: There is a short circuit in a harness. There may be a problem with a connector. Repair the wiring and/or the connector. Replace part, if necessary. Verify that the problem is resolved.STOPTest Step 4. Check the Harness for an Open Circuit
Remove both termination resistors from the CAN data link.
Fabricate a jumper wire that is long enough to create a test circuit across the connector for the termination resistor. Crimp connector sockets to each end of the jumper wire.
Use the jumper wire in order to create a short circuit between terminals A and B on the tee's connector for the termination resistor that is located between the P1 ECM connector and the customer connector. This will effectively replace the termination resistor with a short circuit.
Measure the resistance between terminals P1-50 (CAN data link +) and P1-34 (CAN data link -).
Remove the jumper wire.
Use the jumper wire in order to create a short circuit between terminals A and B on the tee's connector for the termination resistor that is located on the customer's harness after the engine interface connector. This will effectively replace the termination resistor with a short circuit.
Measure the resistance between terminals P1-50 (CAN data link +) and P1-34 (CAN data link -).
Remove the jumper w