2005 E46 M3 electrical issues

[Ollyd]

Hi Chaps,

Question for you experts out there.

Currently running the above M3 (with 50k on the clock)and have a growing issue. For about a year now the battery light has been flickering on an off (very briefly) and intermittently. Took it to the local Stealer whilst under warranty and surprise surpirse they repeatedly found no faults but suggested it might be the alternator. No faults logged on the cars computer.

Recently the car has developed another more worrying but probably linked problem. When starting from cold the car goes in to an engine safety mode with three warning lights on: Battery light, EML and Traction control. The engine will hardly rev even when applying a lot of throttle and it’s also missing occasionally like it is not firing on all cylinders.

If I turn it off after about a minute of this and then restart it runs fine - although very recently it has been taking longer and longer to get it to run normally from cold.

Had the car serviced the other day (service 2) and this did not help so I am guessing it was not dodgy plugs etc.

Any ideas? Alternator, ignition coil, battery of something even more sickeningly expensive!?

Am guessing alternator but don’t want to splash out on one only to find it was something else.

Thanks in advance for any suggestions and help.

[M3RMS]

Did a main dealer do the service, that sounds like that should definitely light up some fault codes. Hell, I had about 15 come up once just because the battery died!

I'd get it replugged into the computer asap, sounds potentially quite bad.

Also log onto mtorque, those fellas will give you some good pointers pretty quick.

Good luck.

Edited by M3RMS on Friday 24th July 22:02

[dan101smith]

If it's showing warning lights then it should be logging error codes.

Get it on a diagnostic machine asap - even someone with Carsoft or similar should be able to help you.

[Carfiend]

M3RMS said:

Also log onto mtorque, those fellas will give you some good pointers pretty quick.

Good luck.

When they fix their outgoing mail so you can register I expect they will be very helpful.

[Jake.]

I'm pretty sure it'll be the alternator. They are a pretty common fault on these cars around the 50k mark.
Mine went at 48k miles and when searching on the net I found a massive thread on one the US forums with loads of guys that had had the same failure at similar mileage.

I replaced mine with a new, genuine BMW one but it was expensive. IIRC it was £369 for the part and 2 hours labour to fit it (God knows how it takes them 2 hours to replace an alternator though, looks fairly straightforward to me)