[Scud]

What exactly is it ?

I thought it was to turn traction off but the traction light still flashed when in snow.

Thanks

[335ier]

If you press it once it is only semi disabled. Press and hold for 3 seconds ish and its totally disabled.

To be honest you wont be gaining anything except revs if you do.

[AlanQS]

I don't suppose the search button works very well on this subject since people call it by so many names.

You have DSC on the car which is the nanny state, stopping power to the wheels and flashing it's little light at the slightest excuse.

Pressing the DTC button briefly puts up the DTC light on the dash. All this does is delays the onset of DSC by a certain margin. If you like, it will tolerate more wheel-spin before "applying the brakes" so to speak (cutting engine power to the rear wheels).

Holding the DTC button in for about five seconds switches DSC off, almost entirely (in extremis, it will still operate) which means lots more wheel-spin tolerated with a concomitant reduction in safety which has to be replaced with driver skill. With DSC totally off, it can be surprising how dodgy the car can feel, you can't just drive it the way you would with DSC operating.

With snow, the full DSC comes on so easily you often find you can't move because the moment the wheel slips it cuts power and this is not what is wanted. But if you are sliding all over the place with virtually no grip at all, even when you have switched DSC off, it will operate when things get bad enough - hence the flashing light.

[dxb335d]

Fully disabled it does NOT still operate'
!!! At all

[HighlandPete]

Originally Posted by Scud

What exactly is it ?

I thought it was to turn traction off but the traction light still flashed when in snow.

Thanks

Pushing the button once engages DTC (Dynamic Traction Control). This allows a bit more wheel spin, beneficial for in snow.

Worth watching this video from Tirerack. Note the comments from about 2 minutes onwards, comments on traction control and acceleration.




HighlandPete

[AlanQS]

Originally Posted by dxb335d

Fully disabled it does NOT still operate'
!!! At all

"330i, 330d, 335i, 335d; in the same way as with a differential interlock, brake intervention takes place on the rear axle if the drive wheels spin severely, improving forward momentum even if the DSC is disabled."

From BMW themselves, Page 75 of the Driver's Manual.

[mjh93sa]

http://www.e90post.com/forums/showthread.php?t=45216

.. just one of the many threads discussing it.

[Scud]

Thanks for the indepth replys guys really clears it up for me. Thanks.

I haven't searched as of yet because it's doesn't have the option on the iPhone but again thanks for clearing it up for me.

Cheers
Scud

[NFS]

Originally Posted by AlanQS

"330i, 330d, 335i, 335d; in the same way as with a differential interlock, brake intervention takes place on the rear axle if the drive wheels spin severely, improving forward momentum even if the DSC is disabled."

From BMW themselves, Page 75 of the Driver's Manual.

Default position = DSC engaged - All safety functions available. On snow, as soon as the wheels slip you will lose engine power, which makes progress difficult.

Press DTC button briefly = DTC engaged / DSC Restricted - The safety functions are all still available, but they will not act as quickly. This allows some wheelspin on snow, without cutting engine power.

Press and hold DTC for 5 secs = DSC disabled. Directional and stability systems are no longer available (except for ABS).

The wording you are quoting from the manual is new and was not in earlier e90 manuals. It suggests that the ABS module will brake driven wheels under severe wheelspin (even with DSC de-activated) to try to replicate the actions of a locking differential.

[m1bjr]

I had my new 318 stall this week in ice and snow.
Plenty of spin with DTC on, but at low rpm I guess the brake activation was enough to stop the engine!

[ASR1]

Originally Posted by NFS

Default position = DSC engaged - All safety functions available. On snow, as soon as the wheels slip you will lose engine power, which makes progress difficult.

Press DTC button briefly = DTC engaged / DSC Restricted - The safety functions are all still available, but they will not act as quickly. This allows some wheelspin on snow, without cutting engine power.

Press and hold DTC for 5 secs = DSC disabled. Directional and stability systems are no longer available (except for ABS).

The wording you are quoting from the manual is new and was not in earlier e90 manuals. It suggests that the ABS module will brake driven wheels under severe wheelspin (even with DSC de-activated) to try to replicate the actions of a locking differential.

Could this potentially kill one of the drivetrain sensors (e.g. ABS)?

I ask because I am getting a control system failure message after spinning the wheels trying to get out of snow, with DSC/DTC fully deactivated.

[HighlandPete]

Originally Posted by ASR1

Could this potentially kill one of the drivetrain sensors (e.g. ABS)?

I ask because I am getting a control system failure message after spinning the wheels trying to get out of snow, with DSC/DTC fully deactivated.

A BMW system can typically reset after excessive spinning, once used on a decent surface again. Not sure how much distance is required but sure someone who's had it happen will confirm. My Passat would reset after a few metres, on the next start up.

Brother in law's XJ had to be recovered after the same thing happened, wouldn't allow a restart.

HighlandPete

[mjh93sa]

Originally Posted by ASR1

Could this potentially kill one of the drivetrain sensors (e.g. ABS)?

I ask because I am getting a control system failure message after spinning the wheels trying to get out of snow, with DSC/DTC fully deactivated.

Hopefully the car has just become completely confused. After a period of time it has decided that the rear wheels can't really have done 1/2 a mile more than the front ones (or something equally daft) and that in fact the sensors on the front wheels have failed.

Having seen a few cars go on a dyno, they got horribly confused in what are basically very similar conditions. After running properly again without all that "wheelspin" the system can see that actually all is well and reset itself.

Hopefully it is this and not an actual failure.

[dxb335d]

Fully disabled is fully disabled.

[NFS]

Originally Posted by dxb335d

Fully disabled is fully disabled.

Thats right. You still have ABS though and the latest manuals seem to be saying that you also retain some wheel braking under 'severe wheelspin'.

Can't say I have noticed this though?