Hey guys first post on the forum! Thanks. So here’s the deal full tran

sparency

TLDR: I tried installing a headunit without disconnecting the battery and now the car will not crank or turn over. Has viper alarm system. Anti theft light is solid.HELP!

Hello guys! I’m having a bit of trouble with the hummer. Let me first start out by saying the previous owner had put a viper alarm in with remote start. I want to know if I should take it to a shop and have them check the BCM

So yesterday I was replacing the headunit that the previous owner had installed (outdated touchscreen). I took out the connections for the old wiring harness , each were soldered so I clipped them. Everything was fine.

With the headunit out and the bezel covering the headunit our (4wd control hazards disconnected). I drove to advanced to get some supplies for the install. Came back home wired up the harness that was previously installed on the old head unit it was a GMOS. Plugged it in then nothing. So I found that whoever installed the system used an auxiliary power source from under the dash to get the headunit power. I connected the 12v power to the unit and still nothing, up until this point I had been turning the car on and starting it up to check to see if it was the issue. After I connected the wire my alarm went off and now the anti theft light is on and the truck will not start. Not crank , not anything . All dash lights come on and off as usual. AC works all functions except starting. I think I might have fried the BCM but I have no clue. I also think it has something to do with the viper alarm.

Things I have done-

For viper alarm:
Turned off valet mode
Disconnected the “brain” or computer for the viper alarm
Pulled the fuse for the viper alarm and put it back in

For Hummer:
Waited ten minutes for the fuel pump to reset
Checked my fuses for bcm and starter (I don’t have a volt meter to test the relays)
Disconnected the battery for 30 min

I am at a total loss and feel like a complete idiot for not disconnecting the battery. I’ve heard of something called a “starter kill” on viper alarms that I can bypass but I really don’t want to cut anymore wires. I absolutely need this truck I just moved away and really don’t know anyone who’s good with electrical issues in cars. Sorry for the long post hope you can help

Thanks,
-Andrew

 

https://www.hummerforums.com/forum/h...ination-28481/
read Hummerz post

 

Wow, you pulled a blast from the past. Btw, still oe and in service to this day, without issues. Fretting; easy to correct:

 

And can you enlighten the dunce like me? Where and how should the electronic cleaner be applied?

 

I Tried the relearn method still nothing. I went out and bought a jump box and a multimeter. Battery is at 11.3v. I’m still trying to wrap my head around all this because it was working just fine before alarm went off. This morning I had gotten in and the light was flashing just as you said on the relearn instructions. This was new because the past times I looked at the anti left light it was solid. Now there is no light.