will a noisy possibly faulty alt. cause stalling and engine lite to go on?

The pulley on the alternator has probably got a bad bearing. That would be the chattering. If the alternator itself is going bad, you will get a multitude of electrical failures all over the vechicle going in and out. Get alternator tested but with the bad pulley you will probably have to replace it anyway.

have codes scanned to see if they pertain to low voltage issues