Car takes 5 mins to start - what's the issue?

[Shaoxter]

My E60 M5 has been developing an annoying issue recently, actually it's been going on for a few months but has got worse I think.

If I don't use the car for more than a day or two, turning the ignition key doesn't do anything and the car doesn't try to start. During this time the yellow engine warning light is illuminated. After I leave it for 5 mins the car starts up and drives just fine and there's no warning lights or anything.

I've taken it to a main stealer aleady and paid them £100 for telling me "I'm not driving the car enough". Which is true most of the time since it's not a daily car but the same thing happens no matter how long/short my previous drive was.

So any ideas? Battery, alternator, just a sensor, or something more substantial?

[Shaoxter]

Battery hasn't been replaced in 4 years at least, but I don't have access to another battery to test. Even if I did I'm under the impression that the car needs to be re-coded to recognise a new battery.

What's strange is that it never fails to start, seems like the car just needs a few mins to wake up.

[Shaoxter]

Thanks jcolley, that's great info. I'm booked in for a service in a couple of weeks and if it doesn't get resolved by then I'll tell them to look at that.

Session8 said:

I've found the odd occasion when it does happen if I just lock the car from the remote key fob whilst in the drivers seat, give a few seconds then unlock she normally fires up straight away.

I was thinking of a worn key barrel but it's happened on either set of keys and as mentioned it only happens if it's been several days since I've driven her.

Also good suggestions, I've never used the second key so will give that a go.

[Shaoxter]

Thought I'd update - car has been with BMW for a couple of weeks and they're recommending a new battery (current one is 9 years old), apparently everything else looks ok.

What's annoying is that it's not covered under warranty and they want me to fork out for a new battery before testing it again...

[Shaoxter]

Well got a new battery fitted and the car starts straight away now, even after leaving it at Stansted during the easter weekend.

[Shaoxter]

Ok so quite a few months later the issue came back... after putting a new battery in it was fine all throughout summer but during the recent cold spell it started acting up again.

What's weird is that it appears to be temperature dependant (i.e. gets worse as it gets colder) and perversely, it gets worse if I've taken it on long drives rather than short ones.

Anyway I got the fault codes read out. Of course Sod's law meant that they could not replicate the issue...

[Shaoxter]

Coolio, will check all those connections. Have checked the battery connections already and they were fine.

Will the 9FED have anything to do with this? A bit of googling shows some people mentioning the steering angle sensor (although I have no idea why this would affect starting...)

[Shaoxter]

Ok so the garage is saying it's the CAS module, seems like you were right from the start jcolley (how on earth do you know so much about this??)

They didn't mention anything about swapping the DME as well though, apparently they can special order the CAS (requiring my V5 and ID etc.) and program it? Does £500 for that seem reasonable?