Check Engine Light... Now Dead (UPDATED 1/22)

[X5_2_OBX]

The 'Check Engine' light came on in my mother's E70 last week. She booked an appointment a few days out to get it checked. She went to take it in that morning and the light was off. The service manager said not to bother leaving it which was frustrating because they are usually very good about taking it and looking it over anyway.

Fast forward to today- she's sitting at a red light and the car dies. She tries to restart the engine... makes a gawdawful sound but won't start. The headlights are on and not at all dimmed and there were no other signs of a battery problem. I can't describe the sound it was making but it was nasty sounding. Since it was darn near stopped in the middle of the intersection BMW Assist rushed the tow truck which showed up in about 30mins. In the meantime, my brother remembered that the service department was still open but only for 15 more minutes. We booked it over there and they gave us a 325i loaner... otherwise we'd be screwed!

Anyways, I tried to look up to see if anyone else has had this problem and it sounds like another member may have experienced something similar but I couldn't find any follow-up on it. Any thoughts?

[rufusdedog]

The "gawdawful sound" is worrisome. Let us know what the dealer finds.

[lsh]

So the service dept looked at the car today and it starts and runs fine. They will keep and drive it another day, but now I'm quite concerned about driving around a car and having it die on me.
If anyone has had this problem or knows what it might be, please share!
One thing - I don't think the gas mileage is as good as it was - for city driving anyway.

[StumpyPete]

I had a similar problem with my E53 once. IT was due to using some low-grade fuel (Uk supermarket). Since then I have used nothing but high grade (RON 97 or above).

[lsh]

I thought of that, but we already only use the highest grade of a well known brand. The tank was more than half full. I've had probs before with much older Saab fuel pumps and gas in the winter that showed when tanks were low.

I'll ask service if I can safely try a gas additive in case I got a bad fill. I wonder if they test for that?

[lsh]

The car died on the mechanic and had to be towed in.

That's good news so now they can figure it out and we won't live in fear of another breakdown.

They suspect fuel pump power but still trying to solve it.

[X5_2_OBX]

UPDATE (1/22):
They told us a few days ago that the floorboards were damp. It turns out that there was a leak in the air conditioner (I believe it was a hose) which caused some wiring to get wet and corrode which ultimately led to the car dying in the middle of the road.

My guess is that this was a progressive problem that was worse over the summer when the a/c was actually being used and just manifested itself now as the wires continued to corrode.

They say everything is fixed and ready for pick-up tomorrow morning.

We'll be watching things very carefully to make sure this hasn't caused any more damage.