My 06 325xiT, with comfort acccess has my mechanic scratching his head. On two occasions, my wife (with her key) couldn't get the car to start. Idiot lights come on, nav screen lights up, but no cranking at all. She tried it with the key inserted, still nothing. I drove to her location, tried my key, still nothing. Called the tow truck. While we were waiting a cab driver offered a boost. We hooked it up, let it charge for a few minutes, it started right up. I drove straight to my mechanic, we stopped and restarted the engine without a problem. He did a load test on the battery, it failed, and was replaced under warranty.
I drove home, abut six hours later, my wife tried to start it, no go again. I tried to jump start again, no cranking with either key. I noticed this time, that while the idiot lights and nav screen would come on, after ten seconds or so both would go dark. Called the tow truck again, an arrival at the mechanic's garage, they unloaded, and it started right up.
We left the car with him for a week, it started up every day. They printed up diagnostic reports, sent them out for analysis, no errors found. He suspects it might be the Intelligent Battery Sensor (the block right by the battery + terminal, but couldn't be sure this was the problem. I declined the $430 gamble to replace this, and drove the car home without incident. The mechanic thought my wife's key might somehow be the culprit. She had a couple of low key battery warnings a couple of months ago, but not recently (I replaced batteries in both keys just in case).
This week, after seven months with no problems, it happened again. This time it was still doing at the shop. I also noted that the steering wheel lock stayed locked when I pushed the start button. It's in the shop now and they are running PIN codes. Anybody else experience anything like this?