Key fob, alarm issues, maybe BCM

[ChitownCraig]

Key fob and alarm issues. I locked my car with my key fob as usual, when I went to unlock it with my key fob it wouldn't unlock, the key fob wouldn't respond to any inputs. I used my key to unlock the door and of course the alarm went off with the horn and lights flashing. This is a factory alarm. I tried to start the car and nothing. I pulled both horn fuses from underneath the hood to quiet it down. I changed out the battery on the fob and that didn't work.

I disconnected the battery to see if it would rest the alarm for ten minutes, and it did to a point. I tried using the key fob again to see if the key fob worked and it didn't for about a minute after reconnecting the battery, but then work correctly. On the DIC display it said Alarm Activated by Hotwire. The car did start after this finally. But after driving for about ten minutes on the highway the Airbag fault message came up for a few seconds, the speedometer dropped out, but came back and then the low tire light icon came on. The tire icon light went off after about two minutes of driving. After driving for another ten minutes the ABS fault message came on along with the X Contact dealer and the tire light icon. This time all the gauges dropped out for about twenty seconds and the came back to normal. After driving for another ten minutes the low tire light went off. The car drove fine the whole time. I haven't tried the key fob or starting the car since I got home. The car battery is only two years old. Sorry for the long post, hopefully it's something simple.

I left the car unlocked last night, tried the key fob this morning and it didn't respond. I tried starting the car and it wouldn't start. Just a whole bunch of waring messages again. Abs fault, brake, air bag, contact dealer.

[Markmsf3]

If I had to guess, I'd say you need a new battery. Seems I've read this before and it's always the battery going dead. Many electrical gremlins have been fixed with a fresh battery.

[ChitownCraig]

If I had to guess, I'd say you need a new battery. Seems I've read this before and it's always the battery going dead. Many electrical gremlins have been fixed with a fresh battery.

Battery checked out good.

So I put the battery back into the car and still a whole bunch of the same DIC messages. I tried to start the car several times. I eventually got the key fob to pop the trunk, so I figured I would try to start the car...It started right up for about 10 seconds then it turned it's self off with warning messages in the DIC again ABS fault, contact dealer and tire pressure. The radio turned on with the car as well then turned off with the car. Tried to start the car again but just warnings now. When I went into enginering mode it shows info now on the sensors, but I think it's froze on from when the car started for those 10 seconds. Also my Atari gauges, light around the ignition, the lights around the heated seats/tc and window switches are lite up now and won't turn off. Those have been lite up for about 10 minutes now. I put the battery on my battery tender attached to the car.

[ChitownCraig]

Back to another update for today, which I think we might of figured it out. I left the car battery on the battery tender all night attached to the car. I went to use my key fob and it actually worked, unlock, trunk. I went into engineering mode and battery voltage was 12.1, scroll down to battery charge and it reads 0. All of the other info in engineering mode read correct except for tire pressure which read 148. I'm assuming because I haven't driven the car. Looks like it's the battery, even though it passed the battery test yesterday at the store.

[Markmsf3]

99% of the time when all that craziness happens electrically, it's the battery even when it 'checks' out ok.

[WhatNext]

+1.

Had a car that wouldn't start, dragged the battery with me just to re-cycle it. (might have been the G8) They checked it and said it was still good. I said "dump it".