Cummins ISX CM870 (2003-06) Fault Code: 598 PID: P167 SPN: 167 FMI: 1/1 Electrical Charging System Voltage – Data Valid But Below Normal Operating Range – Most Severe Level. Very low battery voltage detected by the battery voltage monitor feature.

Make sure the ECM battery supply (+) is coming directly from the battery and not the starter.

Possible cause:

1)Undercharged batteries caused by a malfunctioning alternator or regulator.

Possible repairs:

1)Charge or replace the battery.
2)Repair or replace the alternator and/or OEM wiring to the alternator.
3)Repair or replace the OEM harness.
4)Repair the battery power connector.