How do i reset the service charging system message on my 99 cadillac deville?

Charging voltage should be around 14 volts or more for battery to be properly charged. If significantly below that the alternator is not working properly.

You are on the right track...the battery will only allow the car to run a few minutes if the alternator is not re-charging the battery while running...most parts stores will test your alternator for free...on your Caddy, the alternator is held on by three mounting bolts...be sure to disconnect your battery before working around the alternator. Inspect your alternator belt...(serpentine) may also need replaced...some used to call this belt the 100,000 mile belt...I recommend changing mush sooner...check for cracks and worn edges etc. Hope this helps.

maybe the fuel pump is bad? or fuel injectors may be dirty? maybe running some fuel systems cleaner will help? please give me 100% rating i only need 2 more :)

Sounds like a faulty voltage regulator to me.Start the car and take a multimeter and check voltage coming out of the alternator it should be 14-14.6 volts if its not within these specs take alternator back and get a new one.

was the new alternator a re-manufactured one,(they have been known to be faulty)

need to check the wiring and connections for corrosion or damage

SOUND LIKE ALTERNATOR VOLTAGE REGULATOR FAULTY MAKE SURE DRIVE BELT NOT SLIPPING AND ALTERNATOR ELECTRICAL WIRES NOT LOOSE OR DAMAGED.

alternator is overcharging the battery replace alternator

Yep, check or change your alternator.

So you have a new alternator. I S IT CHARGING ? If the answer is yes , and the battery still dies, I would say there is a 12 volt drain in the electrical system. Hope this helps