Cummins ISB4.5 CM2150 Fault Code: 597 PID: 167 SPN: 167 FMI: 1 Electrical Charging System Voltage – Data Valid But Below Normal Operating Range – Moderately Severe Level.

Posted by PerDiezel Solutions on January 20, 2026

Circuit Description
The electronic 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 ECM power harness. This direct link provides a constant power supply for the ECM. The location of the battery will vary with the 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 a calibrated value.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK 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 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 unswitched battery supply is coming directly from the battery and not the starter.

Possible Causes
-Undercharged batteries caused by a malfunctioning alternator or regulator.
-High-current devices on the vehicle such as citizens band radio amplifiers, numerous exterior lights, or other accessories.

Cummins ISB4.5 CM2150 Fault Code: 596 PID: 167 SPN: 167 FMI: 0 Electrical Charging System Voltage – Data Valid But Above Normal Operating Range – Moderately Severe Level.

Cummins ISB4.5 CM2150 Fault Code: 585 PID: SID 39 SPN: 677 FMI: 4 Starter Relay Driver Circuit – Voltage Below Normal or Shorted to Low Source.

Cummins ISB4.5 CM2150 Fault Code: 584 PID: SID 39 SPN: 677 FMI: 3 Starter Relay Driver Circuit – Voltage Above Normal or Shorted to High Source.

Cummins ISB4.5 CM2150 Fault Code: 559 PID: 157 SPN: 157 FMI: 18 Injector Metering Rail 1 Pressure – Data Valid but Below Normal Operating Range – Moderately Severe Level.

Cummins ISB4.5 CM2150 Fault Code: 559 PID: SPN: 157 FMI: 18 Injector Metering Rail 1 Pressure – Data Valid But Below Normal Operating Range – Moderately Severe Level.

Cummins ISB4.5 CM2150 Fault Code: 556 PID: 101 SPN: 101 FMI: 0 Crankcase Pressure – Data Valid But Above Normal Operating Range – Most Severe Level.

WARNING!