a couple things, i wonder if they're related...

first off, all of a sudden when my car comes up to temp, my voltage drops to like 11 or 12, and will go as low as 9 depending on driving conditions. i figured it's just the alternator dying with heat. it puts off a strong 14 volts when the car is stone cold. BUT...

My coolant gauge would always jump around, start off seeming ok, and then jump way too high when it warmed up, but the car never got hot and the new (apparently and the old) CTS works fine. the fan still comes on at the appropriate temp although the gauge doesn't reflect that.

so I put a new temp sending unit in there the other day, and noticed that the wire was all cracked up and shorting on another wire (a wire for my AC clutch, which is probably why that burned up last summer). so i fixed it up with some tape and a piece of loom for now. well, it stopped jumping around, but it seems to DOUBLE the actual temp. by the time its at 230 or so (wherever the fan turns on) the thing is PEGGED WAY past 280... but the car isn't hot at all.

so, while i'm driving it around after the temp sender unit was in (only to discover the above)... my check engine light comes on all of a sudden. wtf... it seems like these things are linking together, like its one problem causing all of them. so i pull a code 32... digital EGR and/or a short in the wiring

it seems to me as if i might have a short somewhere, grounding out on something, that i can't see... does anyone know any common wiring that may cause any of these things to link together like this? any other ideas? or do you think it's just the low voltage giving me the EGR fault, and the temp sender is still a whole other problem?