2002 Cooper S we've had her a couple of years she's probably run 3 or four months. Have had the clutch switch replaced twice, battery replaced twice, starter replaced, ecm reflashed, immobilizer was replaced also I believe, and the keys reprogrammed of course. After each fix she runs for a little while and then suddenly won't start. I can turn the key and hear the proper buzzing like powering up sounds but nothing happens beyond that when I try to engage the engine. For a while I could leave the key turned in the number 2 position for 30 seconds to 5 minutes and she would start up but now that's not working either. I'm desperate at this point does anybody have a clue or a trick I can try? This getting stranded thing is old!!

 

You need to test for a draw, remove + battery cable and connect a test light with everything turned off. If it shines you have a draw, start removing each fuse until the light goes out, when it does see what that fuse powers then go to work disconnecting each unit until you find it. I can take a while so be patient.