[TDF9]

ABS light.

INPA says code 5DB0 - left rear sensor.

I found corroded wires to the sensor plug (from the car side), and spliced & soldered in a new sensor plug (used the BMW kit for this). Code remains.

I swapped out the sensor for the right rear one, which is new and not throwing codes. Cleared codes. ABS light & 5BD0 return immediately.

I tested the resistance on the new plug, and with the ignition on, it reads 668 Omhs. Per other threads, I gather this is normal.

I took apart the new plug and tried connecting the wire connectors directly to the ABS sensor wires - in case the plastic plug housing somehow wasn't leading to a solid connection. Cleared codes. ABS light & 5BD0 back immediately.

So I feel like I've verified the car side plug is showing the correct resistance, and eliminated a bad ABS sensor as a variable. What am I missing?

Thanks for any thoughts or advice!

[335i54n]

physically trace the wires back to abs unit, test the wire to abs unit and last you could swap pins and see if it the abs module. since you found corrosion once more than likely that your issue

[TDF9]

Thanks!
Am following your advice, and have traced back to the rear seat side bolster so far.
The plug into the abs module seems to have more than one blue and brown wire pair entering it. Anyone have a map to the pins, or know where to getone?

[335i54n]

once it enter the cabin you should be good, did you check the other side or front values to compare. i would double check your solder, funky problems are usually do to small things

[TDF9]

All my tests showed solid continuity on both hot and ground wire from inside the cabin to the ABS sensor plug (zero resistance). So I finally pulled the big plug out of the ABS module under the hood, found a map to the pins, and even there had continuity all the way back to the sensor. Great, but also... ugh.

Per your suggestion, started down the path of swapping pins into the ABS module, left rear for right rear sensor wires, to see if the fault would switch sides. But the plastic in the big ABS plug is super brittle, and one of the clips holding it together snapped, so I gave up in fear.

I may have to take another run at that.

I see lots of stories online of people whose pumps have failed, but they give off different codes. No one seems to have had my "bad sensor, left rear" 5BD0 code and had a bad ABS module. So I think I must be missing something. I just can't think what.

I completely take your point about bad / iffy soldering, and agree that seems most likely. But I feel like I've ruled that out now.

I also checked all the ABS fuses in the glove compartment (all fine, naturally).

From a quick look, replacing an ABS module seems like a can of worms (coding), so I'm hoping that's not my fate.

Mostly venting, but if anyone sees something I've missed, please point it out!

[Andystobbs]

If you've still got the old plug, with some useable (un corroded) wire, attach it directly to the ABS module by cutting the wires near abs module. Wouldn't mess about trying to move pins if the plastic is brittle.
Seems silly but its 100% fool proof way of ruling in or out the abs module.

[TDF9]

I ended up swapping pins (after tracking down a pin tool - thx, Amazon).

5DB0 error remains (left rear sensor), and no 5DB1 (right rear sensor) appears. So I guess that means the error is at the source, the ABS / DSC module, and I'll have to find a used one - or perhaps send it in for repair.

Still feels odd that this one specific part of the module would fail, with no other warning signs. I wonder if a short in the circuit - likely at the sensor - could have somehow caused this in the module?

Anyway, that's where things stand. Thanks for all of you who have weighed in to help

[TDF9]

Originally Posted by Andystobbs

If you've still got the old plug, with some useable (un corroded) wire, attach it directly to the ABS module by cutting the wires near abs module. Wouldn't mess about trying to move pins if the plastic is brittle.
Seems silly but its 100% fool proof way of ruling in or out the abs module.

Almost did this, but without the rest of the harness attached to the ABS module - among other things, supplying power to the module - I didn't think I'd read any error codes. Also realized that I didn't have to disassemble the giant plug, I could pull out specific pins - provided I have the right pin tool...

[Andystobbs]

Sorry I didn't mean attach it to the ABS module pins themselves, rather to the wires coming from the ABS module plug, while it was plugged in.

I didn't phrase that too well. If you buy a used module, just plug it in and verify progress before bothering to unbolt any hydraulics.

Also on a RHD it is just possible to remove the electronics and leave the complete valve block fully connected hydraulically.
Might be do able on LHD too. Save bleeding the brakes.

[TDF9]

I'm completely stumped.

Bought a new (used) DSC module, and plugged it in before installing (and before opening up the brake lines). No change: same 5DB0 error, among others. So I did not install it.

I just tried splicing in an the ABS sensor directly to the sensor wires in the left rear seat bolster - again - just to double check / completely rule out s something funky in the wiring closer to the wheel. No change.

It seems clear the DSC module is getting no signal at all from the sensor. When I clear codes in INPA, the 5DBO error returns immediately. So it's not like a reluctor ring issue that shows up once the axle is turning.

Yet I've swapped the leads to left and right rear sensors at the DSC module, and the error remained left rear.

I wish I understood at a deeper level what this 5DBO error is really saying, what conditions trip it. Anyone have an idea, or know where to read deeper up on how systems like the ABS / DSC work?

[TDF9]

Problem solved: in the end, it was a faulty wire connection - specifically the plug into the ABS sensor. I thought I tested for that, twice, but evidently I didn't do it well - as a replacement gray plug from the junkyard solved the issue.

I had used a BMW sensor plug replacement kit, the blue one (only one they offer). I know blue is for brake sensors, but understood the FCP Euro website comments to mean the blue plug could also work for ABS sensors. I think that was not true - perhaps the internal pins are not deep enough or something.

Just share in case that helps others: the blue BMW replacement plugs don't work for ABS sensors, or at least they didn't for me!