[PPPPage]

I'm going to try not to be long-winded here.
My car occasionally needed a jump for the past 6 months (just shy of 90k right now) so I'm considering battery replacement anyway. Take the battery to auto store a block away, tests out at 10V, i walk away with a replacement.
I may have accidentally hooked it up backwards for about 1 full second. this was enough time for something underneath the engine (not in the fuse box next to the battery) to spark and throw a little smoke.
Well, sh*t. I noticed that i did something very stupid and proceeded to hook them up properly. Car starts up but the battery light is on.
Engine is running fine, belts are turning, but multimeter registers less than 12V at battery connections while car is running, suggesting alternator not charging.
Take the alternator to the same auto store, tests okay. Twice.
Youtube video guy says original alternators sometimes test okay but in actuality are not functioning properly, so i replace anyway.
I hook the new one in, connections are all good, car starts up just fine.
I still have the battery light on - and battery posts still register just under 12V while car is running
Look for fusible link between alternator and starter that maybe fried - but it's just a solid wire running between, no fuse or link of any other kind.
Removed harness from alternator, connection looks okay, registered .7 ohm (honestly don't know what that's supposed to be, but it seems fine?).

What else could i have caused that would keep the battery from being charged by accidentally (and very temporarily) reversing the polarity?

 

[DrivenDaily]

Oy vey!

The BCM controls the alternator's output. Hooking the battery up backwards could have fried some very critical component within the BCM.

I hate to say this, but if you can't find it, you may need to pony up some $$$ and have it diagnosed. You may be able to fix it yourself afterward, or maybe not.

I feel really bad for you, especially if you're trying to keep costs at a minimum.

 

[PPPPage]

So my next question is, can I test that without removing it? I started to get in there and have a look but it seems I need to remove a chunk of the dash to get to the top screw...
Replaced the radio fuse already, so there's that..

Oy vey!

The BCM controls the alternator's output. Hooking the battery up backwards could have fried some very critical component within the BCM.

I hate to say this, but if you can't find it, you may need to pony up some $$$ and have it diagnosed. You may be able to fix it yourself afterward, or maybe not.

I feel really bad for you, especially if you're trying to keep costs at a minimum.

 

[PPPPage]

hold that thought about the dash, i've got the BCM out. it's very stubborn about coming apart to visually inspect the board within, is there a way to test this?

So my next question is, can I test that without removing it? I started to get in there and have a look but it seems I need to remove a chunk of the dash to get to the top screw...
Replaced the radio fuse already, so there's that..

 

[DrivenDaily]

The BCM is in the front of the center console. I've heard of others sending theirs in for repair, but since I haven't needed to do that myself, I don't know if the repairs worked or not. You can use the Search feature, or the Advanced Search to help you find who and where they were sent.

 

[PPPPage]

ok so i put the BCM back, replaced the fusible link between the alternator and starter and BOOM i'm getting full recharging volage to the battery.
however, the battery light is still on. diagnosed a couple other blown fuses (radio amplifier for one, causing no turn signal sounds or radio or "key left in ignition" beeping), and all systems seem to be working... except the remote. can't lock or unlock or remote start, and that is seemingly the only thing that's still happening, aside from the light still being on. does this still sound like the BCM? (hoping for a "no" here..)

Oy vey!

The BCM controls the alternator's output. Hooking the battery up backwards could have fried some very critical component within the BCM.

I hate to say this, but if you can't find it, you may need to pony up some $$$ and have it diagnosed. You may be able to fix it yourself afterward, or maybe not.

I feel really bad for you, especially if you're trying to keep costs at a minimum.

 

[DrivenDaily]

That sounds very promising!

There are 3 fuse boxes. Check the fuses in all 3 and you just might find one last victim of Battery Cable Reversifying. I hope that's all it is.

 

[PPPPage]

yup i've been through all three and believe i've got any fuses in those taken care of. the battery light is still on (though all voltage reads as good), and my remote doesn't work. i'm thinking (and kinda hoping at this point, to avoid it being the BCM) that i need to get into the remote receiver in the trunk, and hopefully i'll find a fuse there. I'm also going to have a look at the battery current sensor, as if that wasn't working, i'm hoping it would cause that light to remain on, despite systems seeming to work properly. we'll see, i'm getting into all of that tomorrow.

 

[DrivenDaily]

The battery current sensor is a loop that the negative cable(s) must go through. If it's hooked to the battery's negative post, it must go through that loop or it could turn on the CEL.

The rear fuse block has the fuse for the RCDLR — remote control door lock receiver. The RCDLR itself does not have the fuse. It is RKE/XM, Fuse 16, 7.5 Amps.

The physical location is on the rear package shelf, under the plastic cover. There are no moving parts in that area at all. Here is what my 2011 looks like with the rear shelf removed. The RCDLR is that gray box in the center. At the left edge of the image is a metal box that's bolted down, which is the XM tuner.

If you wanna check to be sure it's getting power and ground, be careful, since the same plug also has GM LAN wires. Testing them with a standard probe could cause new issues. On the plug, Ground is Black on pin #1, Power is Red/White on pin #4. Pin numbers 2 and 3 are the GM LAN wires.

 

[PPPPage]

ok so the problem is solved, lol. the last two issues are just symptoms of me being an idiot.
when i replaced the fusible link between the alternator and starter, i moved a bunch of wires and stuff out of the way, including the harness on the alternator (i mean, it's right above that wire i needed to replace, so i just wanted some room to work so i didn't have to pull the alternator off just to do that).
well this morning, i tested the leads on the current sensor and was getting resistance values within normal range so i figured that wasn't it (plus how would reversing the battery polarity affect a sensor that doesn't actually receive current in-line from the battery?) so i thought maybe i'll test the sensor on the alternator - then i started swearing at myself as i noticed that after i replaced the fusible link, i was concentrating more on testing with that in place than i was MAKING SURE EVERYTHING WAS HOOKED BACK UP. so i put the harness back in place on the alternator, started it up, battery light went away, all voltage tests nominal. FINALLY

oh and the remote not working was just me again being a dummy. when i pulled fuses out of the trunk box to check them, there were so many empty and unused spaces, i just put the remote receiver fuse back in the wrong spot. when you actually listed the fuse number and it's amp rating, that was what clued me in on that, so a huge THANKS to you, sir.

all is well now, i accidentally replaced a part (alternator) i may not have needed to, but i did it myself, provided myself with a small project which is nice during this time of quarantine, and learned more about my car. wins all around (save for maybe the $240 unnecessarily spent)

 

[DrivenDaily]

That's good news, and reassuring that hooking it up backwards doesn't necessarily mean that expensive parts start frying.

And thanks for coming back to share the solution. That earns you an Atta-Boy!

 

[RedLTZ6]

ok so the problem is solved, lol. the last two issues are just symptoms of me being an idiot.
when i replaced the fusible link between the alternator and starter, i moved a bunch of wires and stuff out of the way, including the harness on the alternator (i mean, it's right above that wire i needed to replace, so i just wanted some room to work so i didn't have to pull the alternator off just to do that).
well this morning, i tested the leads on the current sensor and was getting resistance values within normal range so i figured that wasn't it (plus how would reversing the battery polarity affect a sensor that doesn't actually receive current in-line from the battery?) so i thought maybe i'll test the sensor on the alternator - then i started swearing at myself as i noticed that after i replaced the fusible link, i was concentrating more on testing with that in place than i was MAKING SURE EVERYTHING WAS HOOKED BACK UP. so i put the harness back in place on the alternator, started it up, battery light went away, all voltage tests nominal. FINALLY

oh and the remote not working was just me again being a dummy. when i pulled fuses out of the trunk box to check them, there were so many empty and unused spaces, i just put the remote receiver fuse back in the wrong spot. when you actually listed the fuse number and it's amp rating, that was what clued me in on that, so a huge THANKS to you, sir.

all is well now, i accidentally replaced a part (alternator) i may not have needed to, but i did it myself, provided myself with a small project which is nice during this time of quarantine, and learned more about my car. wins all around (save for maybe the $240 unnecessarily spent)

so i pretty much did the same as you, i put the battery backwards after i had it recharged after replacing my alternator. now my battery light is on. so your solution was that the connection to your alternator was not hooked up? so it was basically running on the belt and thats it?