Cummins ISC CM2150 (2007-09) Fault Code: 343 PID: SID 254 SPN: 629 FMI: 12 Electronic Control Module Warning Internal Hardware Failure - Bad Intelligent Device or Component. ECM power supply errors have been detected.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.

Make sure the ECM unswitched battery supply is coming directly from the battery and not the starter. If unswitched power is coming from the starter, it is possible for the battery voltage to drop low enough during cranking to set this fault active.

This fault can also be caused by resistance in the ECM battery supply (+) or (-) circuits. Resistance in these circuits can cause the voltage level at the ECM input to drop low enough to set Fault Code 343 active.

Possible repairs:

1)Tighten the loose connections and clean the terminals.
2)Charge or replace the battery.
3)Repair or replace the OEM harness.
4)Replace the blown fuse(s).
5)Repair or replace the OEM power harness from the OEM power connector to the batteries.
6)Repair or replace the ECM power harness.
7)Repair or replace the OEM harness.
8)Replace the ECM.