This diagnostic code is associated with the CAT Data Link. The FMI 9 means that the ECM has determined that an abnormal update has occurred.
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 wires
The 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 no shorts between the +battery and 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 the +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.