I have a 2004 Malibu--actually I just got it. When I test drove it I did not turn on the radio so I did not notice the problem that the radio won't shut off after I turn off the car and remove the key. Neither does the light on the gauge. I had to turn the engine on and off again and again to shut them and even that stopped working after while. I took it to a mechanic who made me a new key and seemed to fix the problem but after two days it was doing the same thing again! This time I took it to the mechanic and paid $400 to have them change the part they thought was malfunctioning (the tumbler assembly if I remember correctly). Again, it was fixed on the site but went crazy after I got home. This time I couldn't even remove my key! By the way, I just put in brand new battery into the car since the old one wend dead.
Anybody has any idea what might be wrong? Really appreciate it!

 

Ok, i had the same problem and what was actually happening was the key wasn't turning all the way to the lock position. This was happening bc of the neutral safety cable attached to the ignition switch just disconnect that.

 

I just wiggle my shifter a little bit. This problem plagued me for a little while and caused my battery to die a couple times. Just move the shifter from back to front until it clicks when you put it in park.

 

I just had this happen tonite to my 99 suburban. I removed the large 30A fuse in the fuse box and that did the trick. It is called "accessory". The radio works with the key on. We'll see tomorrow if I disabled anything important.