0390449 JOHNSON COVER,By-pass

Table 1
Diagnostic Codes Table    
Description     Conditions which Generate this Code     System Response    
248-9 @CatDatalinkLong@ not communicating     Communication was lost for two or more seconds.     The code is logged.    The Cat Data Link is used for communication between electronic modules. The Cat Data Link is used to communicate information from the Electronic Control Module (ECM) to other electronic systems. The Cat Data Link is used for programming and troubleshooting the ECM.The ECM communicates with Caterpillar Electronic Technician (ET) in order to share status information and diagnostic information. Cat ET can also be used to configure the ECM parameters. This information will not be available if communication fails between the ECM and Cat ET.
Illustration 1 g01286073
Typical schematic
Illustration 2 g01156133
P1 ECM connector (P1-8) Cat Data Link + (P1-9) Cat Data Link −
Illustration 3 g01234146
Location of ECM connectorsTest Step 1. Inspect the Electrical Connectors and the Wiring
Turn the "main disconnect switch (MDS)" to the OFF position.
Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the connectors to other modules on the Cat Data Link. 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 ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.
Check the harness and the wiring for abrasion and for pinch points.Expected Result:All of the connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.Results:
OK - The harness and connectors appear to be 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. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.STOPTest Step 2. Check for Shorts in the Harness
Disconnect ECM connector J1/P1 at the engine ECM.
Disconnect any control modules from the Cat Data Link.
Disconnect Cat ET from the service tool connector.
Measure the resistance from P1-8 to every terminal on ECM connectors P1 and P2.
Measure the resistance from P1-8 to the chassis ground.
Measure the resistance from P1-9 to every terminal on ECM connectors P1 and P2.
Measure the resistance from P1-9 to the chassis ground.Expected Result:The resistance measurements indicate an open circuit.Results:
OK - The resistance measurements indicate an open circuit. Proceed to Test Step 3.
Not OK - The resistance measurements do not indicate an open circuit. There is a short circuit in the harness or connectors.Repair: Repair the connectors or wiring and/or replace the connectors or wiring.STOPTest Step 3. Check for an Open in the Harness
Use a suitable piece of wire to create a short circuit at the service tool connector. Short terminal D and terminal E together.
Measure the resistance between P1-8 and P1-9.
Measure the resistance at the connectors of any other control modules.Expected Result:The resistance measurement indicates a short circuit.Results:
OK - The resistance measurement indicates a short circuit. The Cat Data Link is OK.Repair: If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".STOP
Not OK - The resistance measurement does not indicate a short circuit. There is an open circuit in the harness or connectors.Repair: Repair the connectors or wiring and/or replace the connectors or wiring.STOP