Circuit DescriptionThe 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 LocationThe 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 original equipment manufacturer (OEM). Refer to the OEM service manual.

Conditions for Running the DiagnosticsThis diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault CodesThe Engine Control Module (ECM) detected the battery voltage was greater than a calibratible value.

Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.Conditions for Clearing the Fault CodeTo validate the repair, start the engine and let it idle for up to 5 minutes.The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop TalkThis fault code is part of the Battery Voltage Monitor feature. The ECM can increase idle speed and deactivate idle decrement switch if idle speedup is enabled. Use INSITE™ electronic service tool to view the Battery Voltage Monitor feature settings. Disabling the Battery Voltage Monitor feature will also disable this fault code.

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

Possible cause of this fault code:

Overcharged batteries caused by a malfunctioning alternator or regulator.Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

Possible Cause:1) Battery failure2) Alternator, Regulator, OEM wiring to the Alternator failure3) ECM calibration