Z4 Won't start unless key is in ignition for 10+ mins

[Fishbonze]

Hello everyone i need desperate help with my 2007 BMW Z4. At the moment the car will not start unless i keep the key in the ignition for 10-15 mins or if the car is jumped, i changed the key battery, no luck. Battery and alternator have been ruled out because the battery is brand new and the alternator is charging the battery. starter hasnt been ruled out because the car starts intermediately when the starter engages also took a meter to the starter and it has power. some people have said ignition switch, not sure how to test it...BMW wants $245 just to run the diagnosis which is fine just would prefer not to. The code thats coming up at the moment is 2F45 Interface EWS-DME. When i clear the code the car also fires right up but the code has been persistent now and wont allow me to clear it. Absolutely stumped as someone who is mechanically inclined. Any ideas? Should i just bite the bullet and take it in to BMW? Any help is appreciated.

[Coi]

Before the 15 mins does the car crank and try to start or just nothing happens when you turn the key?

The battery in the key just powers the remote functions (lock/unlock/pop the trunk). There is a separate transponder that tell's the car's immobilizer it's ok to start that doesn't require a battery.

The fact that jumping it makes a difference does make it seem like an electrical issue. Many BMWs won't start if the battery voltage is just a little too low. What's the voltage on the battery when the car is off and what's the voltage when you try to start it? Even though your battery is brand new it might be worth getting it tested in case it's bad. If so should be warrantied. It's also possible you have some sort of parasitic drain or something that's messing with the battery.

Also instead of taking it to the dealer there are a some extremely competent 3rd party BMW repair shops (or just euro car repair shops) have lower labor rates. In fact with older cars like ours I sometimes trust them more than the dealer where technicians may have only been trained on newer cars.

[pokeybritches]

You could try an EWS delete via tuning software.

[3002 tii]

Originally Posted by Fishbonze

Hello everyone i need desperate help with my 2007 BMW Z4. At the moment the car will not start unless i keep the key in the ignition for 10-15 mins or if the car is jumped, i changed the key battery, no luck. Battery and alternator have been ruled out because the battery is brand new and the alternator is charging the battery. starter hasnt been ruled out because the car starts intermediately when the starter engages also took a meter to the starter and it has power. some people have said ignition switch, not sure how to test it...BMW wants $245 just to run the diagnosis which is fine just would prefer not to. The code thats coming up at the moment is 2F45 Interface EWS-DME. When i clear the code the car also fires right up but the code has been persistent now and wont allow me to clear it. Absolutely stumped as someone who is mechanically inclined. Any ideas? Should i just bite the bullet and take it in to BMW? Any help is appreciated.

Stupid questions…

1. Is this the case for both keys?
2. Does it only happen on cold starts (i.e. after you get it going, does the car start up fine are you shut off and retry immediately)?
3. Auto or manual?
4. During that 10 min waiting period, what position is the key in?

Our cars are getting to the age where even well-kept examples start succumbing to age related issues, biggest culprit being wiring. I would check wiring connections to DME and EWS to make sure nothing is frayed, loose, etc.