Cummins ISB4.5 CM2150 Fault Code: 598 PID: 167 SPN: 167 FMI: 1 Electrical Charging System Voltage – Data Valid But Below Normal Operating Range – Most Severe Level.

Circuit Description
The engine control module (ECM) receives constant voltage from the batteries through the unswitched battery wires that are connected directly to the positive (+) battery post. The ECM receives switched battery input through the vehicle keyswitch wire when the vehicle keyswitch is turned ON.

Component Location
The ECM is connected to the battery by the OEM harness. This direct link provides a constant power supply for the ECM. The location of the battery will vary with each OEM. Refer to the OEM service manual for the battery location.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes
The ECM detects that the battery voltage is less than 8-VDC.

Action Taken When the Fault Code is Active
– The ECM illuminates the red STOP ENGINE light and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code
-To validate the repair, start the engine and let it idle for 1 minute.
-The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.
-The ECM will turn off the MIL after three consecutive ignition cycles that the diagnostic runs and passes.
-This fault code and MIL can also be cleared with INSITE™ electronic service tool.

Shop Talk
This fault code is part of the Alternator Failure Warning feature. The ECM can increase idle speed and deactivate the idle the decrement switch if Idle Speedup is enabled. Use INSITE™ electronic service tool to view the Alternator Failure Warning feature settings. Disable the Alternator Failure Warning feature to disable this fault code.

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

Possible Causes
-Undercharged batteries caused by a malfunctioning alternator or regulator.