I've been going through this exact scenario recently and because we don't drive the X much, it is VERY intermittent. I did go back through my notes and I found that I replaced the ignition switch (which I ended up finding the old one in the new box) and got a new key from the dealer and that seemed to fix the problem, but now that we have been driving it a bit more (the i3 does not do well in snow) the no crank/no start has reared it's ugly head.

So what I think I am reading here in this thread is that the key must be the culprit and not necessarily the EWS or ignition switch? I have been using the old key only because it worked almost 98% of the time and I didn't want to use the new one unless I needed to, we just needed a factory spare. Once the X is back from the shop, I'll try using the new key and see if we have any issues with that one. Again, since we don't drive it often, the response may be a bit of a wait.

Cheers!

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2004 X5 4.4 Build 01/04 Alpine White on Schwarz Dakota Leather, Anthracite Headliner
Xtrons Android HU, SPORT PKG, COLD WEATHER PKG(W/REAR HEATED SEATS AND HEATED STEERING WHEEL), CONVENIENCE PKG, FACTORY HITCH