40021 2 Mercruiser NUT (M6)

Illustration 1 g01726100
Schematic for the CAN data link
Illustration 2 g01458450
Pin locations on the P1 connector
(20) CAN+
(21) CAN- Test Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF position.
Thoroughly inspect the harness connector P1/J1 and any other connectors in the circuit for the CAN data link. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the CAN data link. Refer to Illustration 2.
Check the harness for abrasion and pinch points from the keyswitch to the Electronic Control Module (ECM). Expected Result:All connectors, pins and sockets should be completely coupled and/or inserted. The harness should be free of corrosion, abrasion and/or pinch points.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Perform the following repair:Repair the connectors and/or the wiring, or replace the connectors and/or the wiring. Ensure that all of the seals are correctly in place and ensure that the connectors are completely coupled.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.STOPTest Step 2. Check the Data Link Terminating Resistance
Disconnect connector P1 from the ECM.
Measure the resistance between P1:20 and P1:21. Expected Result:The resistance is between 50 and 70 Ohms.Results:
Result 1 - The resistance is between 50 and 70 Ohms. This is the correct resistance. The fault may be in the connection to other devices on the data link. Proceed to Test Step 3.
Result 2 - The resistance is less than 50 Ohms. There is a short circuit in the harness.Repair: Repair the connectors or the harness and/or replace the connectors or the harness.Ensure that all of the seals are correctly in place and ensure that the connectors are completely coupled.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.STOP
Result 3 - The resistance is between 110 and 130 Ohms. One of the terminating resistors may have failed.Repair: Locate the two terminating resistors and remove the two terminating resistors from the harness. Depending on the application, one or both of the terminating resistors may be located in other ECMs on the data link.Measure the resistance of each terminating resistor.If one of the terminating resistors is incorrect, replace the faulty terminating resistor.If each terminating resistor is between 110 and 130 Ohms, proceed to Test Step 3.
Result 4 - The resistance is greater than 150 Ohms. There may be a break in the harness. Proceed to Test Step 3.Test Step 3. Check the Data Link Wiring
Disconnect each of the connectors that connect other devices on the data link.
Use a multimeter in order to measure the resistance between P1:20 to each of the CAN+ pins that connect other devices on the data link.
Use a multimeter in order to measure the resistance between P1:21 to each of the CAN- pins that connect other devices on the data link. Expected Result:The resistance of each wire is less than 2.0 Ohms.Results:
OK - The resistance is less than 2.0 Ohms. Proceed to Test Step 4.
Not OK - Some resistances are more than 2.0 Ohms.Repair: Repair the connectors or the harness and/or replace the connectors or the harness.Ensure that all seals are correctly in place and ensure that the connectors are completely coupled.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair has eliminated the fault.STOPTest Step 4. Check the Other Devices on the J1939 Data Link
Use the appropriate service tools in order to diagnose other devices on the data link. Refer to the troubleshooting guide for the machine. Expected Result:The other devices are working correctly.Results:
OK - The other devices are operating correctly. Restart the diagnostic process.STOP
Not OK - The other devices are not working correctly.Repair: Use the appropriate service tools in order to diagnose other devices on the data link. Refer to the troubleshooting guide for the machine.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.STOP