Thread: Key won't turn after battery discharged following heavy rain - is it the BCM?

I love my Fatty (2008 4.2 SC V8). I truly do. Having said that I am ready to burn it in the driveway.

My latest problem is this:
1) After heavy rain, I went to start the car. The battery (which is brand new) was flat.
2) I have had this issue once before - a major drain after wet weather. Then, the car would start after charging the battery - no problem. It would just drain again overnight. I had an auto electrician pull all the electrics in the rear recess (where the DVD player etc.. lives) and pretty much check everything was good. He cleaned all the connections, put it all back together and my beloved Fatty has run fine for the last 12 months. He didn't know exactly what the problem was then though. We were all just glad the problem seemed to have evaporated.
3) This time after some really heavy rain and the battery discharging, after I charged the battery, when I went to turn the key, I could only turn it about 10 degrees. That wasn't the case 12 months ago (when I could turn the key and the car would start). There was no clicking or anything else.
4) The car was unlocked when the battery drained. The central locking isn't working now.
5) Certain things still work, like the headlights, rear door solenoid, interior lights, hazards etc... but certain things don't - like the central locking and the deployable side steps don't deploy when I open the passenger side door (they do when I open the driver's side).
6) The steering lock is not deployed so I can move the steering wheel freely.
7) I tried the "wiggle the key and hold it as far over as possible for 30 seconds" trick to no avail.
8) I've also removed fuse 18, left it out for a minute, replaced it and tried to turn the key - again to no avail.
9) I did notice that there were a few drops of water around and in the dash fuse box - so I'm presently running a fan heater to dry that out. It isn't soaking but who knows how much moisture is too much. Maybe that'll work - I truly hope so.
10) My gut feeling is that something is stopping the immobilizer from recognizing the key but that's pure speculation. Maybe the BCM has gotten wet? I'll be getting that out next to have a look.
11) I don't think it is anything mechanical because before the battery died everything worked just as it should. Sparked up first time, every time.
12) And, yes, I'll be taking it to the garage to get scanned if I can't solve the problem here. I do find that the answers given here are really helpful to the mechanic/auto electrician though. They save a lot of time and unnecessary work - so a huge thanks to you all.

I don't suppose anyone would have a spare BCM they'd like to sell me?

Would anyone please be able to help as it is driving me crazy. Bottle of good red to anyone who can!

Originally Posted by AlmorWalton

And the good news is.... after running the a little heater in the car overnight she is back to normal!


Now I just have to find how water is getting into her when it pours.

Does she have a sunroof?