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.

I had a similar thing happen on my 03 Zo6 ABS unit.  There is a company that fixes the electronics but mine was determined unrepairable.  No units in all the usual places so a junk yard used unit was bought and installed.  Luckily it worked but a lot of unknowns and stress in the search and install hoping for the best.  With as cheap and multiple sources of electronic fuel injection, aftermarket ECUs etc are I hope the industry fills the ABS gap with programmable designs that aren't $3-4k.  Even electric power steering aftermarket is gaining ground.  Brakes and ABS for older non ABS equipped cars, track cars and ABS equipped factory cars can all benefit from some aftermarket support that doesn't break the bank.  AEM,Motec,Holley etc.. should be able to make a unit that is programmable like their ECUs and can be swapped in place of a OEM ABS unit.

This is why 'older' German/European cars seem to just fade away from sight.  Yes, it's not just limited to only them, but you get the idea.  If parts were 1) available 2) didn't need 'special' programming and 3) were within the normal owner's budget, then maybe, possibly, potentially, on a good day, one just might see more European cars here as they get older.  Also, I need to add one thing: the added complexity of BMW's systems (like the cooling system for example) is ridiculous in my opinion after owning a mid-2000's 328 and fiddling with all of the O-ring junctions and snap-together foolishness.  The end result is less of them on the road because no one wants to mess with them much anymore.