Trouble starting in the cold

2005 LGT

17X,XXX miles

5MT

 

1. Last week during a cold sub 20F night the car died and I thought it was the battery. So I got a jump, went and bought a new battery, installed it drove home and all was well.
   
2. The dash lit up with "Er IU" but after researching it I just pulled the negative terminal for a bit and then that cleared it.
   
3. Tonight it's again sub 20F and this same scenario has repeated itself. Dash lights are dead. Playing around with removing and re-inserting the key sometimes lights up the dashboard a little more than others but when trying to start the engine I can hear the rapid clicking under the dashboard of it trying to get the starter to start.
   

 

So unless something completely drained my battery (I will have to get it checked just to cross it off my list of possibilities) I'm going to assume it is STILL GOOD. I also wonder if my old one that I replaced may have been replaced prematurely and the cause is something else.

 

My question now is, what is that something else?

So it could be that BIU (Body Integration Unit) but I was wondering if anyone else had this problem and it turned out not needing a new one of those since I imagine it is probably expensive.

 

I searched but didn't get any hits specifically to this.

Just jumped it and it would not stay alive.

Got a theory it's the alternator going bad and for the past week I've been running strictly off the new battery and now it's completely drained.

Easy test. Go get new battery tested and charged. Once charged start car and test alternator output.

I've had an iassue with a click-click-click when trying to start an older car I once had- was a bad negative cable connection to the battery. Not saying this is your issue, but might be worth checking all your connections.