MK20 DSC/ABS Bleed after replacement

[nuc1]

Looking for some help on an issue with the MK20 DSC/ABS module on my 10/01 build M3.
Initial problem:
Speedometer and odometer work intermittently and have DSC/ABS/Handbrake lights on in the dash. Pulled codes from the DSC_E46 module with INPA and got the following:
Error 50: drehzahlfuehler hinten links kontinuitaet (rear left speed sensor continuity).
If I hit a bump just right, the speedo will read correctly for a bit then fall back to zero. So maybe a bad sensor (very rare as its just a hall effect sensor) or frayed wire.

Things I've done:
1. Pulled and cleaned the LR speed sensor (and the other 3 while I was there) with no success. Checked the chassis wiring (as best I could) where it exits under the car. Also checked the DSC module connector for corrosion. None found.
2. Checked brake fluid level. All good.
3. Replaced the LR speed sensor with new. Same issue.

After some googling, looks like the DSC module is failing (somewhat common from what I've read) and needs some TLC. I'm good with a soldering iron but surface mount stuff isn't easy to repair. Found a place online (modulemasters.com) that repairs older MK20 modules. Some threads out there from other sites with satisfied customers.

Has anyone here had this issue? If so, what did you do?

Anyone know how to bleed the DSC module when I get it back. INPA for MK20 only lets you do an "activate DSC" procedure.

Mike

[eacmen]

I would check wiring before replacing the whole unit.

The wiring harness on the MK20 DSC unit should be easy to get to since its in the “drug bin”


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[heinzboehmer]

Anyone know how to bleed the DSC module when I get it back. INPA for MK20 only lets you do an "activate DSC" procedure.

Pretty sure that's the bleed procedure. Been a while, so don't remember the exact name, but the procedure has you hold the pedal while it actuates the pump and solenoids to try and get air out.

Also, you should be able to remove the electronics part (black bit) from the valve body (silver bit) without opening up the hydraulic system. IIRC, it's just four small e-torx bolts holding the electronics to the valve body.

[nuc1]

I would check wiring before replacing the whole unit.

The wiring harness on the MK20 DSC unit should be easy to get to since its in the “drug bin”


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Did that. No corrosion. Looked brand new. Also checked the wires coming out is the body back where it connects to the wheel speed sensor. Looked fine.

Mike

[nuc1]

Pretty sure that's the bleed procedure. Been a while, so don't remember the exact name, but the procedure has you hold the pedal while it actuates the pump and solenoids to try and get air out.

Also, you should be able to remove the electronics part (black bit) from the valve body (silver bit) without opening up the hydraulic system. IIRC, it's just four small e-torx bolts holding the electronics to the valve body.

Ok that’s really good to know. Lots of info for MK60 not so much for MK20 on the web.

Much appreciated.

Mike

[eacmen]

Did that. No corrosion. Looked brand new. Also checked the wires coming out is the body back where it connects to the wheel speed sensor. Looked fine.

Mike

You need to do resistance and continuity check with a multimeter from the sensor connector all the way to the DSC unit.


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[nuc1]

You need to do resistance and continuity check with a multimeter from the sensor connector all the way to the DSC unit.


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Resistance of new wheel speed sensor approximately the same as old one. Continuity check from sensor connector just in front of rear left wheel on body to connector at DSC/ABS module checked SAT. Not much left in the circuit except the DSC/ABS module itself. Still have same error: left rear sensor intermittent. Going to pull the module and ship it off this week.

Mike

[CrookedCommie]

Is it more cost effective to fix the module vs grabbing a working used one?

[nuc1]

Is it more cost effective to fix the module vs grabbing a working used one?

A new one would have the same failure point(s) so no telling when/if it would fail. And would require coding to car. Rebuild comes with *lifetime* warranty and no coding needed. Install, bleed and go. Downtime for car doesn't really matter much as its winter here..... My 2 cents.

Mike

[nuc1]

Just to update this post. Sent the module off and it checked out completely fine. So back to the drawing board. The left rear body harness connector did pass a continuity test...until you jiggled it around a bit. Actually it took a lot of "wiggle" to break the connection but it was repeatable. Cut it off and spliced in a new one. Did the other side as well. Both were definitely showing signs off age (car is a 10/01 build). Cleared codes, started the car and let it run in first gear at idle (car was on the Quickjack) while watching wheel speeds in INPA. Right rear showed about 4 mph. Left rear never moved. So all pointed to the brand new wheel speed sensor is DOA. Swapped left and right wheel speed sensors and yep now right side shows no response in INPA. Awesome. Put the original 22 year old speed sensor back in and works fine. Took the new DOA one and put it back in the box to ship back to FCPEuro.

Part numbers for new body harness side wheel speed sensors (same for left/right rear):
61131392246KT (connector + 2 new pigtails + 2 molex-type connectors that you really don't need)
Fits all e46 rear wheel speed connectors.

To do the repair from inside the car, remove the rear bench seat and both rear door panels. Pull the carpet back a little bit and you will see the grommet the wires go through. Cut the connector off under the car. Cut the wires inside the car and pull the grommet to the inside of the car. Thankfully there is lot of extra wire inside so it makes it fairly easy to splice in the new wires. Butt or solder the wires together. The grommets are sealed with what looks like butyl and was still pliable after 20+ years. Put the grommet back in and fish the wires out the bottom of the car. Insert new pigtails into new connector and connect to wheel speed sensor. And FYI, the pigtail wires are the same color so a multimeter comes in handy for a continuity check.

On a side note, ECUTesting was a pleasure to deal with and the whole thing took about 9 days including weekends. Not needed in my case but you live, you learn.

Mike