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Old 03-28-2009, 12:12 AM
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bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
 
Join Date: Mar 2008
Posts: 20,514
Mein Auto: 02 BMW 525i M54 auto 130K
2002 E39 ASC BRAKE ABS lights on => Diagnostic Procedure & Parts Location

Oh my. My 2002 BMW E39 has these three lights lit on my instrument cluster:
- Triangle (is it ASC or DSC?)
- Brake
- ABS

I see there are lots of threads on this so I'm reading through them, but, they all seem to know already if it's ASC or DSC they're dealing with.

Am I dealing with ASC or DSC?

ASC (automatic stability control) apparently senses 4-wheel differential speeds during cornering and cuts the engine power via a second throttle butterfly valve to help keep you from oversteering and spinning out in wet/snowy/unfavorable conditions. It may also apply the rear brakes lightly in some situations. It apparently doesn't touch the suspension at all. It has been described as ABS in reverse. Reputedly, while ABS controls the braking force at all four wheels, ASC + T controls the power delivery of the engine, and the way the rear differential distributes torque between the two back wheels only.

DSC (dynamic stability control) in contrast, is apparently a suspension-control system which goes beyond Automatic Stability Control + Traction by monitoring steering wheel movement, vehicle speed, transverse acceleration and yaw to register imminent instability when cornering. DSC then intervenes via the engine management system reducing drive torque and activating wheel brakes when necessary to keep the vehicle stable.

Having said all that, how do I know if my 2002 E39 has ASC or DSC?
(I think it's ASC but I need to know before beginning my troubleshooting.)


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