I have a 2003 325i. It has 55k miles. She drives like the lady she was
built to be. I am worried because every once in a while when I hit a
large-ish bump or random unavoidable pothole a light flashes in the
dashboard and the car seems to lose a little power for a second. I think its
the hazard lights indicator.
Here is a link to a picture by my friends over at Bavarian Auto -
that keeps flashing is the one that the Tach needle is pointing directly at.
That's the Traction Control/Dynamic Stability Control light. It means
that the TCS/DSC discovered the wheels going different speeds (due
to the bump/pothole) due to loss of traction. The power loss is a
direct result of the system "letting up" on the throttle to regain traction
on the spinning wheel.
If you were in a more aggressive mode and the car started skidding,
you might note the second step the system takes, which is using the
ABS system to pump the brakes (on an opposite corner) to recover
from the skid.
Turning off DSC won't solve it, but it will confirm that the loss of
power you feel is due to activation of the traction control.
What you're describing can happen if you go over some larger bumps and
are on the throttle because the rear wheels lose grip and speed up
relative to the front wheels. The DSC electronics perceive this as a
loss of traction and retard the throttle in an attempt to restore
traction. That's the loss of power you feel. It's normal.
What's not normal is if you have started to see this more often as of
late over the same stretch of road and the road has not deteriorated in
that time. It's the first sign that certain suspension componentslike
struts and/or shocks are starting to wear out and should be replaced, as
the wheels are hopping over bumps rather than conforming to them.
Some routine maintenance may be in your future.
Doug Vetter, ATP/CFI
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