855676 Mercury THERMOSTAT, (60C/140F)

Table 1
Diagnostic Trouble Codes for the Data Link Circuit    
J1939 Code    Description    Notes    
639-9     J1939 Network #1 : Abnormal Update Rate     Another controller has incorrectly stopped transmitting a J1939 speed request (TSC1) or another controller has incorrectly started transmitting a J1939 speed request.
The ECM will log the diagnostic code.
The engine will not start.    
1231-9     J1939 Network #2 : Abnormal Update Rate     There is an abnormal update rate on the CAN B network.
The ECM will log the diagnostic code.
The engine may not start.    The following background information is related to this procedure:The CAN data link is also known as J1939 data link. The data link is an industry standard for sending data between different devices in the same application.High speed data is transferred via the data link. The data link cannot be accurately tested without complicated equipment. The data link requires a resistance of 60 Ohms between the two wires to transmit the data correctly. This resistance is made up of two 120 Ohm resistors. The two resistors are known as "Terminating Resistors". The terminating resistors should be at opposite ends of a data link circuit. If this resistance is not present, then the data will be intermittent or unreadable.Note: The wiring for the J1939 data link is a shielded twisted pair cable. If the wiring is damaged, the replacement type must be shielded twisted pair cable.
Illustration 1 g02511077
Schematic for the CAN A data link
Illustration 2 g02730831
Schematic for the CAN B data link
Illustration 3 g02453617
Pin locations on the P1 connector (34) CAN A- (50) CAN A+
Illustration 4 g01980934
Pin locations on the P2 connector (21) CAN B- (29) CAN B+Test Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF position.
Thoroughly inspect the 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 are correctly connected. 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 correctly connected.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 the P1 connector and the P2 connector from the ECM.
Measure the resistance between the P1:34 and P1:50.
Measure the resistance between the P2:30 and P2:31.
Measure the resistance between the P2:21 and P2:29.Expected Result:The resistance is between 50 and 70 Ohms.Results:
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.
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 correctly connected.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.STOP
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 the two terminating resistors.If one of the terminating resistors is incorrect, replace the faulty terminating resistor. If the two terminating resistors are between 50 and 70 Ohms, proceed to Test Step 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 to measure the resistance between P1:50 to each of the CAN+ pins on other devices on the CAN A data link.
Use a multimeter to measure the resistance between P2:29 to the CAN+ pin on the soot sensor module.
Use a multimeter to measure the resistance between P2:30 to the CAN+ pin on the diagnostic connector.
Use a multimeter to measure the resistance between P1:34 to each of the CAN- pins on other devices on the CAN A data link.
Use a multimeter to measure the resistance between P2:21 to the CAN- pin on the soot sensor module.
Use a multimeter to measure the resistance between P2:31 to the CAN- pin on the diagnostic connector.Expected Result:The resistance of each wire is less than 2.0 Ohms.Results:
The resistance is less than 2.0 Ohms - Proceed to Test Step 4.
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 correctly connected.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.Expected Result:The other devices are working correctly.Results:
The other devices are operating correctly. - Repair: Repeat this test procedure from Test Step 1.STOP
The other devices are not working correctly. - Repair: Use the appropriate service tools in order to repair other devices on the data link.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.STOP