Cummins ISB CM850 (2003-06) Fault Code: 596 PID: 167 SPN: 167 FMI: 0 Electrical Charging System Voltage High – Data Valid But Above Normal Operating Range – Moderately Severe Level. High battery voltage detected by the battery voltage monitor feature.

Cummins ISB CM850 (2003-06) Fault Code: 596 PID: 167 SPN: 167 FMI: 0 Electrical Charging System Voltage High – Data Valid But Above Normal Operating Range – Moderately Severe Level. High battery voltage detected by the battery voltage monitor feature.

This fault code is part of the Alternator Failure Warning feature. The ECM can increase idle speed and deactivate the idle decrement switch if idle speedup is enabled. View the Alternator Failure Warning feature settings using the INSITE? electronic service tool. Disabling the Alternator Failure Warning feature will also disable this fault code.

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

Possible causes:

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

Possible repairs:

1)Repair the damaged connections.
2)Tighten the battery connections and clean the battery terminals.
3)Charge or replace the battery.
4)Repair or replace the alternator, regulator, and/or OEM wiring to the alternator.