One thing I forgot to mention: When installing the master cylinder I did not bench-bleed it. Initially I did, but I made a big mess trying to install it with the fluid in the reservoir, so I decided to install it dry and then bleed it. Again, the brake pedal feels firm, but who knows what the real problem is.

 

I just replaced a Bosch DSC 5.7 ABS module in my daughters 325xi. Yours sounds like the pressure sensor is shot.

I was able to bleed the new one using a simple brake pedal pump routine and bleeding each line at the wheel. The pressure sensor on the 5.7 I replaced is ok it was the electronic board that fried. Perhaps just buy a pressure sensor.

I put a bunch of info in the thread i started when I was replacing the module including how to adjust the steering angle sensor using INPA. There is a also lot of useful info in the Renault PDFs about the inner workings of this module.

http://forum.e46fanatics.com/showthread.php?t=1078183


Edit: according to the Bosch DSC 5.7 manual I posted in my thread above the pressure sensor cannot be replaced without replacing the whole unit. I don't necessarily buy that. I can take the old one apart tomorrow and let you know if it looks like you can just swap that part. As I recall it looked like it was just threaded into the block.

 

Excellent, I will try and re-bleed it tomorrow. Unfortunately I don't have access to TIS, only the basic Rheingold, but I can activate the DSC pumps for 5 sec. - should be enough. Will follow up.

 

If you read my linked thread I did not need anything special to bleed the pump. I just did one line at a time making sure the reservoir was never low. I could actually see the bubbles coming out from the disconnect/reconnect. Took a while for the rear wheels ( 3 mins of pumping) but eventually they did. In all total I used about 12-16oz of brake fluid bleeding all 4 wheels.The pedal is firm & no errors from the module. I did this with the battery disconnected and ignition off as I wanted fluid through the pump/block and lines before I turned the abs pump on.

In regard to the pressure sensor it is indeed removable and I believe replaceable. It comes off with a 24mm wrench with little force so don't crank this putting it back.


It is a Bosch sensor and has a part number 0265005303.
It has three pins and I suspect we would be able to get ohm readings off the outer two to the center. Not sure what they are meant to be but if you measure the readings on yours I'll compare it to this known good sensor.

Edit: there is a hole at the cone end of the sensor for brake fluid - I imagine if any debris were to get in there the readings would go askew. Not sure how you might flush that out but I would try brake fluid in a syringe - wear gloves.

If you are on this thread looking for a solution or instructions to swap or code the Bosch DSC 5.7 ABS module - I refer you to this thread beginning at Post #8.
http://forum.e46fanatics.com/showthread.php?t=1078183

 

I went to the garage today and tried to bleed the system again. I ran the precharge pump forward and backwards, took out the pressure sensor and put the fitting with the hose in and ran the pump to push out all the possible air. Then I re-bled the system twice. Still I get a little softness at the very top of the brake pedal and I get the DSC pressure sensor test error.

If I press the brake pedal just a little bit while activating the precharge pump I get the "normal" vibration through the chassis and I can hear the pump running. Releasing the brake pedal makes the precharge pump inaudible. This makes me think that the air bubble somewhere in the system prevents from pressurizing it to the specs and throws DSC pressure sensor test fault.

At this point I am throwing in the towel and taking the car in for the proper BMW bleed procedure.

 

You don;t want to try diagnosing the pressure sensor? Before you go to the dealer read this thread first. Bluebee is online so you might ask him - he has been writing about this module for quite a while and has a comprehensive thread.

http://api.viglink.com/api/click?fo...ement and coding ABS Module - E46Fanatics&txt=BlueBee's thread on the e39 forum


Edit: You do realize that every-time you open up the module even to remove the pressure sensor that you are letting air into it. Once you have the fittings sealed the best way to get out any air is to move it to the wheel bleed nipples then you know there is no more air in the system.

When I reconnected the one I just replaced their was an internal abs pressure sensor error - something about a bleed. After I bled at the wheels with the module closed (all the fittings and pressure sensor connected) the error was able to clear and the pedal was firm again - prior to that the travel was long and it was spongy - as if it had air in it - which it did from me opening the module.

2nd edit - just remember you need to bleed at ALL 4 wheels. I was able to get about a teaspoon of air out of each line. It took a while for the two back wheels before the air bubble from the module travelled all the way to the back but it did - this was the case for all four wheels - just got quicker to see the air bubble as the lines got shorter when I moved to the front.

I'm forgetting that you have no idea how I'm bleeding these - I connect a clear 1/4" tube to the nipple. The tube is about 2 feet long and I can see the brake fluid enter and discharge into my spill tin. As I'm watching the fluid discharge since the tube is clear it is very easy to see air bubbles. In all 4 wheels there was a teaspoon size air bubble that eventually bled from each line after I replaced the module. I used to have a one-way valve at the end of the tube so air couldn;t get back up but now I just keep my daughter pumping the brake pedal till it is a steady stream. Since the tube is 2 feet long I can close the nipple before any air gets back into the system.

Here's a pic to a similar setup

 

The pressure sensor reads 0 to 95 bar pressure as I am pressing the pedal - so the sensor works fine. I have a pressure bleeder and can activate the pumps separately through INPA. My problem is that that I have to do it alone and I just can't pump the brake pedals while opening the bleed nipple and activating the ABS Precharge and Return pumps. It is quite frustrating. I just want to fix it and get rid of it. Wagon is not my cup of tea anyway.

 

That's frustrating - I had to wait a few hours till my daughter came home to get her to work the pedal.

I saw these features in INPA and just did the old fashioned brake pedal method knowing the the fluid from the reservoir would get pulled into the module and forced through it to the lines.

There is a one man brake bleed kit at harbor freight but it will only last once - the rubber components inside the pump disintegrate from the corrosive brake fluid - works great the first time though

 

After changing 3 DSC modules, 2 pressure sensors and bleeding the system numerous times the issue was resolved. The culprit was the new master brake cylinder. The fault - "DSC pressure sensor test fault" appears when the pre-charge pump fails to pressurize the system during the brief DSC system test when the brake pedal is fully released. Apparently the position of the piston seal inside the master cylinder at full idle would allow the pressure from the pump to escape into the reservoir, causing the pressure sensor test fault. I replaced the master cylinder again, bled the system and everything works as it should.

I must stress that this problem was extremely difficult to resolve. Numerous BMW techs with GT1 and Autologics were telling me that the fault is DSC module related 100%, I was driving eBay sellers and ABSMasters crazy. Nobody thought that my master cylinder theory was plausible and they thought I was nuts.

Back to normal driving now.

 

BTDT on a few cars over the years. Even as a trained BMW technician one does not want to believe it's the new master cylinder. Albeit after we burn a few hours diagnosing, looking at live data, theorizing, trying something else we come back full circle and replace the master. UGH. E39's are very troublesome in this regard.

Fine point:
Bleeding the brakes with the two person method has proven to be the best way when dealing with a issue and not just regular maintenance.
However one can have a fully bled system and still see trace air bubbles going down the clear (recommended) tube into the catch bottle.
WHY?
Air can sometimes be drawn past the threads in a capillary sucking action around the bleeder nipple and the brake caliper itself.
If in doubt, keep bleeding. The bubbles around the bleeder threads are most usually very fine when compared to bubbles traveling into/through the lines.

 

Good information. Glad you got your problem resolved!

 

I feel like I've become an expert in Bosch DSC 5.7 systems, after all that I've read, researched, and done.

 

Hi, I got all most the same problem. When I press the pedal on the board I get three errors (DCS, ABS, Brake lights). Bmw scanner and IMPA shows me the error 72 (114) pressure sensor. I tried to change two sensors and it did not help me. I tried to clean and change the oil, maybe it is dirty or it has bulb system, it did not help me. Could it be master cylinder or DSC module? I drive same BMW E46 AWD...

 

Problem solved!!! This was the culprit: OEM NUMBER: 61316967601 (Stop Light Switch). Mounts behind the brake pedal!

 

I have the same problem "72 (114) pressure sensor (Offset)" and I tried to replace Stop Light Switch with OEM Number A0015456309 Mercedes. It doesnt help.