2007 Impala 3 problems at once? Anyone guess why?

Your dead battery might be the root cause as both ignition lock and shift lever need power to "unlock". I would suggest not boosting your battery but getting a new one.

You need to charge the battery and have it tested. The chain parts stores will do that for you. If the battery is bad, simple, replace it. If it's good then you have a draw that is draining the battery. Then the real work begins. If no lights are on be suspicious of the amplifier/chime module under the rear package shelf. The one in my Monte Carlo went bad and it will drain the battery in a couple days. When I worked in parts we used to see one every couple months.

Larkbill said:

You need to charge the battery and have it tested. The chain parts stores will do that for you. If the battery is bad, simple, replace it. If it's good then you have a draw that is draining the battery. Then the real work begins. If no lights are on be suspicious of the amplifier/chime module under the rear package shelf. The one in my Monte Carlo went bad and it will drain the battery in a couple days. When I worked in parts we used to see one every couple months.

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A little off topic:

A family member has a 2001 Monte Carlo SS with the non-supercharged 3800 V-6. It is stock and there is no modifications to the car. It has the factory radio system.

For some time, it has been draining the battery overnight. We installed a battery disconnect switch to prevent it. We have pulled our hair out trying to figure out why the battery is draining.

Can you tell me more about the amplifier / chime module under the rear package shelf? It sounds as though this might be the defect that we can't diagnose. Thank you.

I'm sure what goes wrong with the amp/module is that a transistor that is supposed to deactivate it when the ignition is off has failed and it is staying energized. I didn't want to spend the $500 for a new one so I have a switch on the console to cut off the 12v. supply to the amp/module when the car is parked. The rear speakers make an audible pop when it is turned off. I discovered by accident that if you turn the radio off manually before turning off the ignition (or opening the door after ignition off) that the draw is cut dramatically, but not totally. I would bet money that is what you are dealing with.

To wire a switch you need to locate the 12v. supply wire in the plug at the module. It's always on. Then cut it and wire in the switch so you can turn it off when parked. The switch can be anywhere convenient, mine is on the small snap out plate on the console just aft of the shifter. I solder all connections but if you prefer, crimp connectors will work too.