Cummins ISL CM850 (2003-06) Fault Code: 441 PID: SID 168 SPN: 168 FMI: 1 Battery 1 Voltage – Data Valid but Below Normal Operational Range – Moderately Severe Level. ECM supply voltage is below the minimum system voltage level.

This fault code is logged when the ECM battery supply voltage drops below 6 volts.

1)Verify that the ECM unswitched power is coming from the batteries and not the starter or other device. Check for possible weak batteries.
2)If the ECM unswitched battery supply is taken from the starter, check for low voltage during cranking. Low voltage during cranking can cause the ECM power supply to drop below specifications and log Fault Code 441.

Possible repairs:

1)Tighten the loose connections, and clean the terminals.
2)Charge or replace the battery.
3)Replace the fuse.
4)Repair or replace the OEM power harness.