E46 M3 brakes don't feel right? How to tell if it's the ABS/DSC unit

The brakes just didn’t feel right.

Not a sinking pedal, the usual sign of a failing master cylinder, but something just seemed amiss with the brakes on our E46-chassis M3. The pedal felt soft but didn’t go all the way to the floor.

We figured we had two options: ignore it (hey, the car did stop) or investigate further. …

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This might be a good reminder that this E46 M3 is 20 years old now. Still not old enough to legally drink - but it's getting there.

This one turns 21 years old this month!

I think the bigger lesson here: Sometimes I really wish we had a good, dedicated BMW shop here in the greater Daytona area.

But wait, you say, Daytona does have a BMW shop. I have driven past it. 

So far, two for two, they couldn’t help.

Rod bearings? Yeah, not interested in doing that job.

Reprograming the ABS/DSC unit? Yeah, we don’t have the computer for that. 

End result: I get to do the legwork while working remotely with BimmerWorld and Rennie at Redline Bimmers, two dedicated, helpful partners. When I have questions, they’re quick with an answer. A+ partners on every level. 

If only they were a bit closer to us as I came this close to driving to South Florida for the five minutes Rennie needed to reprogram the ABS/DSC unit. 

For those sorts of prices/headaches, I'd just crack open the hydraulics. My guess would be a bad seal that jammed one of the solenoid valves.  Unless it's sealed in some special way (which I know the Germans love to do), seems like it'd be easy to find/replace.  

Rennie said the device can’t be opened. Well, technically I guess you can open anything, but he meant in a non-destructive way. I thought about having the unit ultrasonically cleaned, but simply replacing it seemed like the quickest option once logistics were thought through. 

If that is a M3 MK60 ABS, it is in high demand.  It has become a popular swap for track cars.  It can function standalone and some the M3 units can be flashed with Motorsports software.  Your old control unit might still have some value.