SPN 167 - FMI 1 (Fault Code 598)

SPN167 FMI1 (Electrical Charging System Voltage - Data Valid But Below Normal Operating Range)
Fault Code 598
ISB, ISC, and ISL with CM2150 - ECM Power Supply Circuit

Fault Code: 598
PID(P), SID(S): P167
SPN: 167
FMI: 1/1
Lamp: RED

REASON: 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.

EFFECT: Red lamp illuminated until very low battery voltage condition is corrected.

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 OEM 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 troubleshooting and repair 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 immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code:
The ECM will turn off the red STOP ENGINE light when the diagnostic runs and passes.

Shop Talk:
Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM.

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 with 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 of this fault code:
• Undercharged batteries caused by a malfunctioning alternator or regulator.

Read More:
SPN 167 - FMI 18 (Fault Code 597)
SPN 167 - FMI 16 (Fault Code 596)


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