F1536 Force HEX HD CAP SCREW, 1/4 - 20 X 3/4

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Typical schematic
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P1 ECM connector (P1-34) data link − (P1-50) data link +
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Service tool connector (Terminal F) J1939 data link − (Terminal G) J1939 data link +Test Step 1. Inspect Electrical Connectors and Wiring
Remove power from the ECM.
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.STOPTest 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 between 57 and 63 Ohms.Results:
OK - The resistance is within the range. Proceed to Test Step 5.
Not OK - The range of the resistance is 114 Ohms to 126 Ohms. A terminating resistor is missing.Repair: Verify that two terminating resistors exist on the data link. One resistor must be located on each end of the data link.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
Disconnect the J1/P1 ECM connector.
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 -)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.STOPTest 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 P1-50 (CAN Data Link +) and P1-34 (CAN Data Link -) at the ECM connector.
Remove the wire short.Expected Result:The resistance measurement indicates a short circuit.Results:
OK - There is not an open circuit. Proceed to Test Step 5.
Not OK - An open circuit exists in the wiring harness.Repair: Make the necessary repairs.Verify that the repair eliminates the problem.STOPTest Step 5. Check the Module on the CAN Data Link
Connect the module to another engine.
If the module operates properly on a different engine, there may be a problem with the ECM.
If the module does not function properly on the different engine, replace the module.Expected Result:The module operates properly.Results:
OK - The module operates properly on another engine.Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - The module does not operate properly on another engine.Repair: Replace the module. Verify that the repair corrects the problem.STOP