My Grand AM wont start

When I went to turn the key to start the car all my power to the vehicle shut off. My lights shut off and everything else that has to have power shut off. I thought it was the battery but it wasnt and then we thought it could be the alternator but we changed that out and it still wont start or get any power to anything. I was thinking it could be a main fuse or a bad wire some where. Im kinda lost please email me if you have any info

Check the connections to the BCM to make sure they are tight. There have been problems with these connectors causing everything to go dead. Secondly, check and possibly replace the ignition switch. A bad switch can cause similar problems since it sends a signal to everyting in the car to work!

How did you test that the battery and find out that the battery is not the culprit?
How is your horn sounds? The head lights?

Make sure you have tested the battery with load test type testing or get a known good battery and test it. Make sure that the cable connectors on the battery terminals are tight and trace the cables to make sure they are not loose.

Check the wires to the starter. I had the recall done and they put in a relay. Didn't tighten the wires, even after I took it back 3 times to have them verify they did thier jobs right.

Kevin

My prob turned out to be the battery only car I ever had that would not RUN on a dead battery with a GOOD alternator.Do a load test my bat had 12 plus volts but no amperage.