ABS/DSC Pump working with ignition off

[Dbpiedade]

Hello!

So I’ve been trying to troubleshoot this issue for a while now, trying to make sure I don’t just jump to the module refurb without reason.
A while back, my M3 locked all four wheels (braking), leaving me in the middle of the road. Thankfully no accident came from this, I was able to power through the brakes and get to a safe place to park.
Upon stopping, I noticed there was noise coming from the engine bay even with the key out of the ignition. It was the DSC/ABS pump.
I then figured out by trial and error, the correct fuse to stop it working. It stopped and obviously my brakes were no longer locking, so I was able to proceed home.

My question is, should I just take the plunge and refurb the module, or could there be another culprit?

I was unable to find a similar situation on an E46. Found it on an E39 and it was the ABS relay which E46’s don’t have.

I appreciate any help! Thank you!

[Casa de Mesa]

So the brakes applied themselves while driving down the road?

😶😶😶 yikes

[FBloggs]

It could be an electrical or a mechanical issue that caused the module to lock on.
It could be a bad booster.
it could be bad fluid or lines.
It could be bad pressure sensors on the ABS unit.
It could be a circuit failure within the control module.

Check the codes first.

[bigjae46]

I would check the solenoid near the brake fluid reservoir. The vacuum from the engine to the brake booster is controlled by the solenoid valve which controls the vacuum return line to the intake manifold.

That's likely not your issue if you hear the actual DSC pump running.

[Dbpiedade]

So the brakes applied themselves while driving down the road?

😶😶😶 yikes

Yup. Yikes indeed, thankfully I wasn’t going fast.

[Dbpiedade]

It could be an electrical or a mechanical issue that caused the module to lock on.
It could be a bad booster.
it could be bad fluid or lines.
It could be bad pressure sensors on the ABS unit.
It could be a circuit failure within the control module.

Check the codes first.

I was unable to read codes from the DSC module with INPA. I will try it again as I’m not sure if having the fuse out could cause it. Otherwise, being unable to connect to the module pretty much concludes that’s the issue?

Thank you!

[Dbpiedade]

I would check the solenoid near the brake fluid reservoir. The vacuum from the engine to the brake booster is controlled by the solenoid valve which controls the vacuum return line to the intake manifold.

That's likely not your issue if you hear the actual DSC pump running.

Yes, shouldn’t be that as I can hear the actual pump
running. But that’s good to know, didn’t know of that!

[heinzboehmer]

I was unable to read codes from the DSC module with INPA. I will try it again as I’m not sure if having the fuse out could cause it. Otherwise, being unable to connect to the module pretty much concludes that’s the issue?

Thank you!

Yeah module needs to be powered to communicate with it and read codes.

If it's powered on and you still can't talk to it, then it's likely that the module itself is the issue.

[bigjae46]

Make sure you have the DCAN cable with the bridged pins. You need that in order to read the ABS/DSC module.

[Dbpiedade]

Make sure you have the DCAN cable with the bridged pins. You need that in order to read the ABS/DSC module.

Thank you, I will look into that to make sure that’s not the issue. Not sure if I have them bridged or not

[Dbpiedade]

Yeah module needs to be powered to communicate with it and read codes.

If it's powered on and you still can't talk to it, then it's likely that the module itself is the issue.

Yes, I guess that’s the only conclusion possible, even though I have yet to see similar symptoms for a failed module elsewhere. Closest I’ve seen was on e39’s, that have an external DSC relay, and my symptoms seem to occur when it fails and it stays stuck on closed circuit.