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Crinopet
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8 Posts
Discussion Starter · #1 ·
As with many others, my ABS ACS lights in the dash stay lit, after a long period of intermittent on/off. I have found many reason for this but most common is a faulty wheel sensor. However in my case all sensors measure the same and I can see action on an scoop when the wheel turns, so i assume they're all right.

A dealership in holland suggested that frequently one or more relays in the fuse box are sticking or burnt in. They mentioned two in particular but not specific which ones.!!

Is there perhaps a forum member that has experience with this? Which relays serve the ABS system. Also a "pedal travel" switch on the brake pedal could be at fault, but again, where is this animal as i could not find any switch other than the brake light switch.

Any other suggestion is welcome, off course, as this problem is beginning to annoy me no end. Of all the useless passive safety gear we carry around these days, abs-acs is most valuable and I hate to drive my 2.8 hard in wet conditions without it!

Z3 , 2.8, 1999. 210,000 km
 

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373 Posts
For some reason, MY99 Z3's are prone to this problem. It has been traced, more often than not, to broken solder connections in the control module. For us in the US, an easy fix is to ship the module to Module Master in Idaho. They fix and guarantee for 5 years for relatively short money in less than a week. However that is probably not a good option for you.

Other more daring or experienced owners have successfully taken apart the module and resoldered the cracked connections themselves. It may worth a trip through the Search function to track down those users and contact them directly for more specific tips/instructions.

FWIW I have never come across a diagnosis/fix that involved a stuck relay or a pedal travel switch. YMMV. Good luck.
 

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Crinopet
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8 Posts
Discussion Starter · #5 ·
Thanks guys i am electronically skilled and repair boards normally with ease. But where ismthe controller located?
Hopefully notmbehind the glove box.

I,have meanwhile checked the relays, and found them to be faultless!

Struggling on .........
 

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Crinopet
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8 Posts
Discussion Starter · #7 ·
daven

thanks a lot. found it, how could you miss it!!
the other reports is quite extensive and very informative. I'll open the box and see what can or needs to be done. if any good, i'll report back.
 

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Crinopet
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8 Posts
Discussion Starter · #8 ·
dear Daven,

yes I am on my own, but before cutting things up that can not be fixed any more a last question , if i may.
it seems that the black box needs to be cut open with a fine saw or grinder. is there a good spot, or rather do i need to avoid some area to avoid damaging the interior.
pre warned is twice wiser!!!!!
thanks
 

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Best I can say is check out post #23 on the thread link. Member, Muurahainen, used a dremel rotary tool to open the box. You may want to try and contact him through that forum. I don't have any contact info, nor have I seen the inside of the module. Sorry that's what I meant by saying that you're on your own.
 

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Crinopet
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8 Posts
Discussion Starter · #11 ·
Dear forum,
Repair of ABS ecu turns out to be a piece of cake. I now understand why repair shops charges a moderate amount and give a quick turn around. My z3 from 1999 has an ATE unit m20. If yr light after a period of intermittent on-off stays llt all the time, you may have the same problem as I have solved. First check the wheel sensors, as often described elsewhere. If all ok, lift the ecu of the brake pressure regulator/pump housing. The four little torx can be easily removed with an M4 socket!! No problem at all. Now, look at black box and see that it seems as if a "lid" is glued on the other side of the coils! That lid has to come off.
I used a dremel grinding tool. Use light pressure and short cuts to follow the seam, otherwise the heath of the little grinding disc will melt the plastic and yr cut is effectively closed again. Be prepared to loose a few discs! The wall thickness of the box is about 5 mm at the seam and the pc board is 2 mm away from the box walls, so little risk of damage to the board exists. After cut, break the remaining four points around the boltholes, twisting a large flat screwdriver and the lid comes of; clean the edges in preparation of gluing later.
Now inspect the board carefully with a magnifying glass and look for "dry" solder connections. They occur most at connections that carry the highest current. Hence the two points underneath the "post with the two connectors" is suspect. These were the culprits in mine. Solder them back with a HOT and small tipped iron and all is well. Just be careful that the solder does not run over the gap between the point and the rest of the board. I found two other suspect connections, but i am sure the two under the post are the cause as these carry probably the power supply to the board and coils.
Glue the lid back with eg an epoxy and refit the ecu to the valve block. Please note that the ecu has to verify that the wheel sensors, speed pick-ups etc are all functioning so it takes a few hundred meters of driving before the fault is diagnosed as gone and, finally, the lights extinguish! A vey satisfying job done well.
FORUM MODERATOR, i suggest to post, or crosslink, this note on a more general SBS/ASC thread, but i am uncertain how to do that.
 
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