HUB 3577958 - Caterpillar

Illustration 1 g00530246
System Schematic For CAT Data LinkNote: When a customer communication module is connected to a single generator set, "B+" is connected directly from wire 10. When a customer communication module is connected to multiple generator sets, "B+" must be connected through a diode. Refer to Figure 1.Generator sets use the CAT Data Link in order to communicate with the Customer Communication Module (CCM). The CAT Data Link consists of two wires that connect the GSC+ to the CCM.The possible causes of a CID 248 FMI 9 are listed below.
A short to the battery positive terminal ("B+") of either of the two CAT Data Link wires
A short to the battery negative terminal ("B-") of either of the two CAT Data Link wiresThe GSC+ cannot detect an open in the circuit of the CAT Data Link. The GSC+ treats a CID 248 FMI 9 as an alarm fault. Active alarm faults are shown on the display when the "Alarm Codes" key is pressed. The engine control switch (ECS) is in any position except the OFF/RESET position. Troubleshoot and repair the wiring. See Testing And Adjusting, "Schematics And Wiring Diagrams". Clear the fault from the fault log after troubleshooting is complete.Test Step 1. CHECK THE BATTERY POSITIVE TERMINALS
Ensure that there are not shorts between +battery and either of the CAT Data Link wires.
Turn the ECS to OFF/RESET.
Disconnect both cables from the battery.
Measure the resistance between the positive battery cable and both CAT Data Link wires.Expected Result:The resistance between the positive battery cable and both of the CAT Data Link wires should be greater than 5000 ohms.Results:
OK - The resistance between the disconnected positive battery cable and either of the CAT Data Link wires is greater than 5000 ohms. Proceed to Test Step 2.
NOT OK - The resistance between the disconnected positive battery cable and either of the CAT Data Link wires is less than 5000 ohms.Repair: Troubleshoot and repair the wiring. Repair any shorts between +battery and the CAT Data Link wires. Refer to Testing And Adjusting, "Schematics And Wiring Diagrams". Proceed to Test Step 2.Test Step 2. CHECK THE BATTERY NEGATIVE TERMINALS
Ensure that there are not shorts between the battery negative terminal and either of the CAT Data Link wires.
Turn the ECS to OFF/RESET.
Disconnect both cables from the battery.
Measure the resistance between the negative battery cable and both CAT Data Link wires.Expected Result:The resistance between the negative battery cable and both of the CAT Data Link wires should be greater than 5000 ohms.Results:
OK - The resistance between the disconnected negative battery cable and either of the CAT Data Link wires is greater than 5000 ohms. Stop.
NOT OK - The resistance between the disconnected negative battery cable and either of the CAT Data Link wires is less than 5000 ohms.Repair: Troubleshoot and repair the wiring. Repair any shorts between the disconnected negative battery cable and the CAT Data Link wires. Refer to Testing And Adjusting, "Schematics And Wiring Diagrams". Stop.