E46 M3 SMG - Won't Start

[Hepburn8]

Hi guys,

I've had my E46 M3 for nearly a year and since late December I've had problems with the car starting. My local BMW specialist has had the car in several times and unsurprisingly the fault never occurs when with them!

The problem I'm having is that 60% of the time the car starts fine as always. On other occassions it can take anything from a few turns of the key to a massive 45 mins to start (you can imagine what Mondays mornings are sometimes like!!). I have the car in N with foot on the brake but nothing happens, I just have to keep tyring again and again until it finally starts.

Have tried everything to find the fault from using the spare key to a diagnostic look by the garage (stated issue from gearbox to starter). Eventually it was suggested that I replace to the computer unit and have the SMG gearbox reprogrammed to the cost of c£750. All was fine for 2 days, then you guessed it - car won't start again!!!

Has anyone else had similar issues, if so how did they fix the problem???

[MattOz]

Not had the issue myself, but perhaps it could be a faulty bonnet switch causing the intermittent problem. I'd investigate that one as the next step, because it's a known issue when it comes to SMG's not behaving!

Matt

[Mahogany]

Hi,

Have you tried:

In first gear,
foot on brake,
turn key all the way round (to start engine) but nothing will happen as the car is in first. Hold the key in this position and flick the gear stick to the left to neutral so that the engine starts

[outnumbered]

It's surely most likely to be one of the microswitches if it just intermittently fails to crank at all. Otherwise I suppose it could have some SMG hydraulics problem and it's unable to get Neutral - but if you're not noticing any problems when driving, that seems less likely.

Does your "specialist" know much about SMG ?

Edited by outnumbered on Sunday 18th April 17:29

[mat205125]

outnumbered said:

It's surely most likely to be one of the microswitches if it just intermittently fails to crank at all. Otherwise I suppose it could have some SMG hydraulics problem and it's unable to get Neutral - but if you're not noticing any problems when driving, that seems less likely.

Does your "specialist" know much about SMG ?

I would have hoped that a specialist would have been able to quickly diagnose which (if any) of the required signals are not getting through to enable the car to start.

[Mayboy]

Push the brake pedal harder - sounds silly but it worked for me

[thehos]

I had this with my last smg, tried all of the above, ended up being a starter motor, ouch!

[Gimmick]

Slightly late getting onto the thread but my M3 has started doing exactly the same. Seems that despite the gear lever being in the Neutral position, it doesn't actually select Neural.

Had the car over 3 years and it is the first thing to go wrong.

This morning I tried the normal sequence for about 5 to 10 mins with no joy and finally got out and rocked the car forward and back, not sure if it was coincidence but when I tried again it was in neutral and started first time.

[Schermerhorn]

Ignition switch is the common fault.