I have a 2006 Grand Prix GT my charging system failure pops up every so often after i replaced the alternator dont know why this is happening after replacing the alternator I have never seen this msg before now i replace my battery which was good still cleaned the battery terminals so far now msg but what could this mean?

I had a similar problem with mine ended up being the fusible link on the main battery cable which is located lower right in front of engine if you look down where the wires come out of the wiring harness to the starter you will see the red cable then it will turn into a black smaller wire that is your fusible link I would check that first

Charging System Failure
Refer to Charging System Description and Operation

Electrical Power Management (EPM) Overview
The EPM system is designed to monitor and control the charging system and send diagnostic messages to alert the driver of possible problems with the battery and generator. This EPM system primarily utilizes existing on-board computer capability to maximize the effectiveness of the generator, to manage the load, improve battery state-of-charge (SOC) and life, and minimize the system's impact on fuel economy. The EPM system performs three functions:
• It monitors the battery voltage and estimates the battery condition.
• It takes corrective actions by adjusting the regulated voltage.
• It performs diagnostics and driver notification.
The battery's condition is estimated during key-off and during key-on. During key-off the SOC of the battery is determined by measuring the open-circuit voltage. The SOC is a function of the acid concentration and the internal resistance of the battery, and is estimated by reading the battery open circuit voltage when the battery has been at rest for several hours.
The SOC can be used as a diagnostic tool to tell the customer or the dealer the condition of the battery. Throughout key-on the algorithm continuously estimates SOC based on adjusted net amp hours, battery capacity, initial SOC, and temperature.
While running, the battery's degree of discharge is primarily determined by a battery current sensor, which is integrated to obtain net amp hours.
In addition, the EPM function is designed to perform regulated voltage control (RVC) to improve battery SOC, battery life, and fuel economy. This is accomplished by using knowledge of the battery's SOC and temperature to set the charging voltage to an optimum battery voltage level for recharging without detriment to battery life.
The Charging System Description and Operation is divided into 3 sections. The first section describes the charging system components and their integration into the EPM. The second section describes charging system operation. The third section describes the instrument panel cluster operation of the charge indicator, driver information center messages and voltmeter operation.

Charging System Failure
The BCM and the ECM/PCM will send a class 2 message to the IPC for the CHARGING SYSTEM FAILURE message to be displayed. It is commanded ON when a charging system DTC is a current DTC. The message is turned off when the conditions for clearing the DTC have been met.

You need to have a full vehicle scan done. Not just engine code's . An to do this you need a professional scan tool , not auto zone or advance etc.. Your best bet , take it to a qualified repair shop.

Your charging system is computer controlled . Do you know what DTC'S - diagnostic trouble code's are ? This are all associated with the charging system inone way or another .
DTC B1327
DTC B1328
DTC B1516
DTC P0560
DTC P0562
DTC P0563
DTC P0615
DTC P0621
DTC P0622


https://www.motor.com/magazinepdfs/042010_09.pdf